Biodiversity

Tuesday, May 09, 2006

MORPHOLOGICAL DIFFERENCES BETWEEN CARTILAGINOUS AND BONY FISH


All fishes are classified as vertebrates organisms. Vertebrates organisms are organisms with the backbone. Fishes breathe in through their gills. Abedon (1997) also says that both cartilaginous and bony fishes belong to the kingdom animalia. Sharks, skates and rays are thought to be the examples of the cartilaginous fishes. They are termed cartilaginous because of the absence of the real bone, but their bodies consist of a cartilage. While on the other side bony fishes are thought to be real fish because they contain bones in their body.

Unlike other types of fishes, cartilaginous fishes have strong jaws. The mouth of the cartilaginous fish is found underside of the head, while the eyes are found on top of the head. Cartilaginous fishes also possess the ''two nostrils which are used for smelling'' (Abedon, 1997). As Shark is one example of the cartilaginous fish, they are unable to see the food while entering their mouth. The skin of the cartilaginous fishes such as the sharks, rays and skates is also compared with the sandpaper, because of its roughness. Five to seven pairs of the external gill openings are also found in the cartilaginous fishes. But ghost sharks have the skin which is smooth and one pair of the external gill openings. Fertilization in cartilaginous fishes is internally.

While on the other side bony fishes are termed true fishes. This is because we are familiar with this type of fish. An example of these fishes includes groper, gurnard and snapper. Unlike cartilaginous fishes, bony fishes have bones and one pair of the external gill openings. Its mouth is also found in the front of the head. Bony fishes also possess a tail fin which is equal in both bottom and top portions.

The brain of the ghost sharks is closely related to that of the birds and mammals (Wikipedia contributors). As compared to that of the bony fish, the brain of the cartilaginous is ten times to that of the bony fish. While the brain size of the bony fish is thought to closely relate to that of the human beings, the reason of having such a big brain is attributed to the much usage of energy.

In conclusion, one can say that both fishes, cartilaginous and bony indicate a huge morphological variety. This is because their structural body is totally different, as one considers that the mouth of the cartilaginous fish is under the head while that of the bony fish is in front of the head the head. Even the cover of their body is different; the cartilaginous fish is covered with a rough skin while on the other side the bony fish is covered with the rough skin but not like the one in the cartilaginous fish.

References:
Abedon, T. S. 1997. Ascent of mammals. [Online]. Available from:
Wikipedia contributors. Chondrichthyes [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 05, 13:15 UTC [cited May 08]. Available from: http://en.wikipedia.org/wiki/Cartilaginous

Wikipedia contributors. Bony Fish [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 06, 13: 23 UTC [cited May 08]. Available from:
http://en.wikipedia.org/wiki/Bone


Peter Muvhali
CSIR PTA
0001
Tell no 012 8142133
Fax 012 8423676
E-mail smuvhali@csir.co.za
URL: http://www.blogsoccer-peter.blogspot.com/

SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Most of the species have males and females, that mate and reproduce sexually. They reproduce by laying eggs, while in some insects they reproduce by developing embryo which devolop inside the female and are born after a short gestation. And for those species to do reproduction they have to underwent mating period which is different depending on the type of insect’s species. (2)

"During the mating period for many insect they underwent Courtship ritual. Which they perform to show that they are ready for mating, while on the other insect there did not show any sign or attract male,they are often stroked by males. Males use legs or antennae to stroke females for sex".(2)

There is different method that the insect use to attract mating; it can be regarded as mating calls or courtship. Some insects release gland known as pheromones mostly it happens on intraspecific interaction, while intraspecific interaction species release allelochemicals.all this chemical are known as semiochemicals it is used for attraction, repellents and stimulants of male insects species for mating.(1)

These pheromones are unique for each species to know that there is an insect of the same species which is ready for mating, and it is simple for male species to follow the scent trail. Insect can detect the smell from distance. It was suggested that moth insect can detect the scent close to eleven kilometres. (1)

In some species during the arrival at the female territory male secrete the scent for courtship, and it helps females to access the quality and quantity of the male. And most of the scent or pheromones that the male release are the scent from the flowers.

Insect like butterflies use colours and movement for attraction, male butterflies will be attracted by the coloured imitation of females, while other flies also forms a compact swarms that attract the females.(1)

Other species uses sound for attraction, frogs croak and chucks to attract male frogs for mating and bird sing a song for mating calls. Some insect that use sound for attracting males for mating , are Female grasshoppers, crickets and cicadas males.

Envious, happens in every species, most of the organisms that use signals for mating they have different method to protect their sperms from other male some stay with their mated females to guard them preventing her for mating again. They also extend copulation which prevents other males to mate with her in that period. There is completion for mating in species so they have to prevent other to mate with the species that they mate. some species produce chemicals that plugs the vagina of the female after mating and this give her opportunity for her to mate once while other have genital apparatus that push the arriving sperms back out of the way in the female spermathecae. Because most of the species like to have their own product some have the apparatus that they use to remove the sperms of previous males from females. (1)

In general most of the species that cannot undergo courtship they use pheromones and allelochemicals to attract males for mating while other uses sound to indicate that they are ready for mating. So this method of mating call or signals that they use helps the male insect to identify the insect which is ready for mating, different species know signs and smell the scent for attraction of the species of the same group.


Reference

1. Entomology [Internet] updated 2004 [cited 2006- 05- 08] Available from: http://bugs.bio.usyd.edu.au/Entomology/InternalAnatomy/reproduction.html

2. Encyclopedia Smithsonian; Mating Insects, [internet] [cited 2006-05-08] Available from: http://www.si.edu/RESOURCE/FAQ/nmnh/buginfo/mating.htm

Mr Elelwani Muanalo
NISL- Ecological Informatics Student
CSIR Pretoria
Tel: +27 12 841 2133
Fax: +27 12 842 7024.
Email: http://www.blogger.com/emuanalo@csir.co.za
My bloger URL: http://www.emuanalo.blogspot.com/

MUTUAL RELATIONSHIP BETWEEN PLANTS AND ANIMALS

Most human consider insects as pests except for those who study them and those who admires them. "Insects are commonly regarded as pests include those that are parasitic (mosquitoes, lice, bedbugs), transmit diseases (mosquitos, flies), damage structures (termites), or destroy agricultural goods (locusts, weevils). Many entomologists are involved in various forms of pest control, often using insecticides, but more and more relying on methods of biocontrol"(2).

Most human cannot see the purpose of insects in our lives and many insect are so benefitial to us and our environment (1). Some of the insects help in pollinating flowering plants (for example wasps, bees, butterflies, ants) through the process called cross-pollination where they carry pollen from one flower to another flower. "Pollination is the transfer of pollen grains to the plant-ovule" (1). "An exchange between plants that need to reproduce and pollinators receive nectar and pollen. Population of pollinator insects has been declined and numbers of species of insects are now cultured primarily for pollination management in order to have enough pollinators" (1).

"Insects also produce useful substances such as honey, wax, lacquer and silk. Honeybees have been cultured by humans for honey, although contracting for crop pollination is becoming more significant for beekeepers". Fly larvae (maggots) were used to treat wounds, to prevent or stop gangrene, because they only eat dead flesh. "Insect larvae of various kinds are also commonly used as fishing bait". Still some humans cannot see the purpose od insects in our lives.

There are different types of animals which help with pollination (carrying pollen grains-male- to other plants-female plant) (3). There is pollination by insects like bees which is called entomophily (4) and pollination by animals such as birds or bats called zoophily(5).

Bees goes to a flower searching for nectar and at the same time they help the flowers by carrying the pollen grain for cross pollination while they are not aware. After the bees have collected nectar they convert it to honey. "The bee collects the pollen by rubbing against the anther (found on top of the filament and it is a male organ-stamen) (6). The pollen is collected on the hind legs, in dense hairs referred to as a pollen basket" (6). After bees has got all the nectar it needed from one flower it goes to the other one, while transffering pollen grain.

Bees gets most of their energy from the nectar which is provided by plants, even the herbivorous animals depend mostly on plants for energy since they only eat plants. "When bees are rearing large quantities of brood (7) (young of honeybees collectively), bees will deliberately gather pollen to meet the nutritional needs of the brood" (7). "A honeybee that is gathering pollen is up to ten times more efficient as a pollinator than one that primarily which is gathering nectar and which transfer pollen unawarely" (3).

"Good pollination management seeks to have bees in a "building" state during the bloom period of the crop, thus requiring them to gather pollen, and making them more efficient pollinators. Thus the management techniques of a beekeeper providing pollination service are different from, and somewhat incompatible with, those of a beekeeper who is trying to produce honey" (1).

Plants provide bees with nectar and bees transfer pollen grain from one plant to the other. Some animals lay their eggs in some flowers then the flower will act as a shelter for those eggs. This shows a mutual relationship between plants and animals because both species benefit from each other. Some animals depend mostly on plants for food for example herbivores (cows, rabbits), they only eat plants so without plants they would die. Even to humans plants mostly provide us with oxygen and we provide the with carbon dioxide. Some plants like trees provide shelter to humans by minimizing the amount of wind and soil erosion during rainy days. According to me there is nothing that is useless in this world everything is here for a purpose mostly we as people we underestimate the power of plants while we are not thinking about what are the plants doing for us.

References

1. Wikipedia contributors. Pollination [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 4, 20:22 UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Pollination
2. Wikipedia contributors. Insects [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 08:09 UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Insects
3. Wikipedia contributors. Types of pollination [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 4, 20:22 UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Pollination#Types_of_pollination
4. Wikipedia contributors. Entomophily [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 5, 10:13 UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Entomophily
5. Wikipedia contributors. Zoophily [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 3, 09:26 UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Zoophily
6. Wikipedia contributors. Anthers [internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 28, 13:40May UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Anthers
7. Wikipedia contributors. Brood [internet]. Wikipedia, The Free Encyclopaedia; 2005 Aug 25, 02:08 UTC [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Brood_(honeybee)

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

HOW THE FIRST PLANTS AND ANIMALS EVOLVED AND BECAME DEPENDENT ON EACH OTHER

Plants are the living organisms that grow in the earth and have a stem, leaves and roots. They play an important role in the cycle of nature and without them; there could be no life on the earth. Plants are the primary producers that maintain all life forms or other living organisms on earth. They manufacture their own food during the process of photosynthesis.

Animals refer to any living organisms that are not plant including people. Animals cannot manufacture their own food; they depend on plants both directly and indirectly for their survival, meaning that in order for them to get their food; they have to depend on plants. All animals and the food that they eat can be traced back to plants ( Kazlev, 2002).

During the process of photosynthesis, "plants take energy from the sun and carbon dioxide from the air". They also take water and minerals from the soil and give off water and oxygen. Human beings or animals breathe the oxygen which comes from the plants. Animals and other non producers take part in the process of respiration. Respiration is "the process whereby oxygen is used by organisms to release energy from the food and carbon dioxide is taken out". The process of photosynthesis and respiration help to maintain the natural balance of oxygen, carbon dioxide and water from the earth (Kazlev, 2002).

The leaves of the plants absorb energy from the sun and turn water and carbon dioxide into sugar and starch. "Sugar and Starch provide plants with energy to grow and they also reduce flowers and seed and carry on their other life processes". Most of the animals prefer the leaves of the plants. Plants and animals are complex organisms made up of cells. Plant cells have "thick, rigid walls that consist of cellulose and cells of animals do not have thick as well as rigid walls". Plants need heat from the sun to grow and the climate of the area also plays an important role in the growth or survival of the plants (Kazlev, 2002).

Prokaryotic are the plant fossils known as bacteria. They feed themselves on "the chemicals which are found inside of the water and they are heterotrophy meaning that they do not use sunlight to manufacture their own food, so they eat their food rather than producing the food". They convert food such as sugar into alcohol to get their energy. There is no nucleus inside the cell of prokaryotic organism. Animal fossils are known as a eukaryotic, which means that their cells do not have nucleus (Kazlev, 2002).

Blue green algae are the plants that are found inside the water or ocean. They use sunlight to manufacture their own food and they also create oxygen. They fill the atmosphere with oxygen. Other organisms need oxygen to carry out their life process of growing, feeding, responding, reproducing and they also produce carbon dioxide and the algae also need carbon dioxide to perform their life processes (Kazlev, 2002).

Living organisms are classified as consumers which are animals, producers which are plants or decomposers which are fungi, depending on how they get food. Animals that feed on plants are known as herbivores such as goats and they are called primary consumers. Carnivores like lion are animals that feed on meat and omnivores are animals that feed on both plants and animals, e.g.: human and baboons (Kazlev, 2002).

Environmental limiting factors such as temperature, water, light, competition and soil contribute on the survival of both plants and animals. So every organism needs certain requirements for their survival. Sunlight and rainfall affect plant growth. These two limiting factors can help the plant to grow well and animals leave the habitat where there are a lot of plants so that they can hide themselves from their energy.

Reference:

1. Kohler, S. Plants, [Internet] 2006 May 8, 14:30. UTC [cited 2006 May 07]. Available from: http://www.blueplanetbiomes.org/plants.htm

2. Kazlev.A.M. 2002, PLANT,(land plants) [Internet] 2006 May o8, 14:00.UTC [Cited 2006 May 07, 10:12]. Available from:
http://www.plalaeos.com/plant/default.htm



Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com/

THE PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

Mammals are animals of the class of Vertebratata whose females have milk producing mammary glands for feeding their young; they also have fur (hair) on their endothermic bodies (warm-blooded) 1. The placental and marsupials are mammals that feed their young using mammary glands. So how do these groups of mammals modes of reproduction vary from each another?

Both placental and marsupial animals reproduce through internal fertilisation. Marsupials have an external pouch (marsupium) on the underside where it rears its young2. After fertilisation the young marsupials grow inside a york sac that is formed inside the females womb which provides nutrition to the embryo2. The young marsupials are born in their early developmental stages and crawl to the pouch where they are nurtured till they develop to independent young ones. In the pouch they attach to the nipples to feed on the milk from the mother.

On the other the placentals have their young through internal fertilisation and the young are enclosed by a placenta in the female’s womb. The placenta allows the young to remain within the uterus for a very long time. The placenta is attached to the uterus and is joined to the foetus by an umbilical cord4. It has a high amount of blood vessels and at this point there is a lot contact between the placenta and the uterus to allow for an interchange between the mother and foetus. The mother’s blood and the foetus don’t mix but through diffusion the waste products from the foetus are exchanged in the mother’s circulatory system. The mother removes them via the kidney4. The same happens when they need to exchange of oxygen from mother’s lungs and nutrients from her food4.

The mammalian sexual cycle involves the regular production of a new egg. For the marsupials before the next egg is produced the neonate in the womb is born but for the placentals’ the foetus has to remain the uterus for a long time4. The foetus of placentals secretes a hormone that stops the production of any more eggs during this period. Also the foetus’ tissue has genetic material from the father so immunological rejection can occur by coming into contact with the female. However this does not happen as the placenta takes care of it and the process by which is stopped from happening is not completely understood4. The marsupials don’t have to have such a complex mechanism as their neonates are ejected early enough2. Marsupials are able to avoid gestation complications that are encountered by the placentals.

The red Kangaroo of central Australia is an example of a marsupial. After fertilisation the neonate is ejected after thirty three days, after which the neonate which has more developed front legs crawls to the mother’s pouch and attaches to the teats on the mother’s womb to suckle4. The sexual cycle of the mother starts again and another egg descends into the uterus and she mates and the egg is fertilised. Then the egg’s development is stopped for a while as the neonate in the pouch continues to grow and adapts really fast. After one hundred and ninety the neonate has grown and can get out of the pouch to go venture outside the pouch4. Afterwards it continues to venture while returning to the pouch before eventually venturing out completely after two hundred and thirty five days. In case there is drought the fertilised egg in the uterus remains dormant till there’s rain and good pasture. This begins the cycle once again. A female red Kangaroo can have three young dependent with her each at a different stage of development. One active young that suckles and ventures out, one tiny neonate suckling in the pouch and the fertilised dormant egg, awaiting further development4.

Marsupilals give birth to neonates that are not fully developed as compared to the placental which carries its foetus till they are mature. The neonates of the marsupials are prone to all the hazards in the environment as compare the placentals foetus which is born fully mobile and well developed outside the mother’s womb. This has made the placental method of reproduction a success as compared to the marsupials and made them successful “in colonising the whole earth”4.

References:

1. Wikipedia contributors. Mammal [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 8, 11:25 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/w/index.php?title=Mammal&oldid=52125662.

2. Wikipedia contributors. Eutheria [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 23, 18:31 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/w/index.php?title=Eutheria&oldid=49786602.

3. Wikipedia contributors. Marsupial [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 23, 22:57 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/w/index.php?title=Marsupial&oldid=49825243.

4. Knight, R. BCB Biodiversity chapter 2 Eggs, Pouches and Placentas

(Cited 2006 May) http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/page_171.htm


VINCENT MUCHAI WAIRIMU

Biodiversity and Conservation Biology

University of the Western Cape

Private Bag X17 Bellville

TEL: +27825103190

Email: 2648463@uwc.ac.za

Website:http://www.muchai.iblog.co.za

SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Insects have both male and female species that mate and reproduce sexually. Some insects reproduce by lying eggs while in some the egg hatches inside the female. During other seasons of the year the males are not available to mate with the female but species like aphids still reproduced.

Different insects use different strategies to to attract their mating partners. All these srategies mostly work only where they are reguired, meaning that if the signal is from the female butterfly it will be heard only by male butterflies.Semiochemicals are chemicals that causes interaction between organisms of different sexes. All these semiochemicals serve one purpose, to complete the life cycles of insects. "These chemicals are divided into allelochemicals and pheromones depending on the nature of interactions because the interaction can be either interspecific or intraspecific"(1).

"Allelochemicals are those chemicals that are important to individuals of a species that are different from the source species. These chemicals are also subdivided into different groups depending on whether the respond of the receiver is comfortable with the emitter not the receiver or the chemical is favourable with the receiver not the emitter or is favourable to both emitter and the receiver. Both allelochemicals and pheromones it is always useful to refer to chemicals as arrestants, attractants, repellents, deterrents, stimulants or other descriptive terms. These terms can indicate what behaviour is involved in the response such as a feeding stimulant or flight arrestant. Pheromones are released by a certain species with the effect of having the attraction to the same kind of species" (1).

Insects have different ways they use to attract each other like in the case of the moths. "The female moths have scent glands on the abdomen that secrete pheromones. These chemicals are secreted to attract the male moth. The male moth can detect these chemicals at a distance of four to eleven kilometres. Sometimes the males secrete pheromone just to induce the females so that they mate. Insects like butterflies use colour and movement. The males will be attracted by the coloured imitations of females and in the same time they will be chasing the other male away. Male flies also form a compact swarms that attracts the female" (4).

Sound is also used as a way to attract each other sexually. "The male mosquitoes are attracted to the note or sound produced by the wing vibration of the wing. Female grasshoppers, crickets and cicadas are attracted by the sound produced by their males. Crickets use the burrows to resonate the sound, the cicadas use their large empty space in their abdomen and the substrate vibration helps the leafhoppers to communicate"(4). It is very interesting to see how clever insects are. Especially looking at the different ways the male insects use to protect thier sperms. Some protect them by guarding the female everytime. Some have some chemicals which they put on the female so that she does not mate again until she give birth. Other males use the scoop to sweep other sperms away before they mate.

Reference

1. Nordlund, D. A. 1981. Semiochemicals their role in pest control. [Internet] 2006 May 08; 15:05 UTC [Cited 2006 May 08] Available From: http://ipmworld.umn.edu/chapters/flint.htm

2. Wikipedia contributors. Insects [Internet] Wikipedia, The free encyclopedia; 2006 May 08; 10:23 UTC [cited 2006 05 08] Available from: http://www.ivyhall.district96.k12.il.us/4th/KKhp/1insects/buginfo.html

3. Wikipedia contributors. Neuroendocrine [Internet] Wikipedia, The free encyclopedia; 2006 May 08; 11:15 UTC [cited 2006-05-08] Available From:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7186527&dopt=Abstract

4. Wikipedia contributors. Reproduction [Internet] Wikipedia, The free encyclopedia; 2006 May 08; 14:35 UTC [Cited 2006 May 08] Available From: http://bugs.bio.usyd.edu.au/Entomology/InternalAnatomy/reproduction.html

Dianah Nangammbi
CILLA CSIR
P.O BOX 395
PRETORIA
0001
Tel: +27 12 841 2133
Cell: +27 73 121 3589
Email: dnangammbi@csir.co.za
http://wwwdianah.blogspot.com/

THE DIVERSITY OF FLYING INSECT LIFE THAT HAS EVOLVED

Insects are “invertebrate animals which belong to the group of class insecta” (2). They are the largest and most widely distributed taxon with the phylum anthropoda. There are “about 925 000 known insect species” (1). For example the dragonfly species, praying mantis, grasshopper, butterfly and moth, fly, tree bug, beetle, bees and ant species.

These insects are categorised into flying insects and non-flying insects. The flying insects such as bees, butterflies, grasshopper and dragon flies have developed their own different characteristics. Their characteristics are seen on the arrangement patterns of wings and their flying pattern. The grasshoppers characterised by two pairs of wing i.e. the inner wings which are very-very soft and the hard outer wings. The wings are attached to their abdomen.

The diversity of flying insects is seen with the example of dragon flies characterised by two pairs of wings which flap up and down synchronously. These two pairs of wings is a special characteristic for this insect because it can fly for long distance at a very high speed. The bees which are characterised by fore and hind wings linked together with hooks. Some of the flying insects have wings that can be folded over their back meaning that they can only spread them when in use. The indirect-flight muscle plays an important role in powering the wings for flying.

The flying ability by insects enable them diversify throughout the world. They gained the ability to explore more territory and find new kinds of food giving rise to more species. Insects easily produce large number of off-springs hence they need only small amount of food. This is another thing which able them to be more than other animals.

These flying insects are also ecologically essential. They play a vital role and they are beneficial to the environment and to humans. Ecologically “they facilitate the pollination process for plants that need to reproduce” (2) for example bees; butterflies receive rewards of nectar and pollen. They play a role in seed dispersal from one point to another. The evolution of different flying insects is very crucial because they produce useful substances such honey, wax and silk. Many insects have been cultured by humans for many years. For example, Locusts serve as food for human.
Insects serve as food for other animals that are feed on insects thus insects are important in the food chain cycle.

Although the flying insects are diversified, they are facing threats. Through pesticides large numbers of insects are killed, although most tend to have some forms of resistance. These flying insects like locust are diversified in such a way that it is possible for them to invade a large portion of land.

Flying insects are very important to other plants and animals. In plants, this is seen during the process of pollination. Some plants cannot reproduce without the aid of the insects. Insects serve as food for other animals for survival.



References

1. A pair of wings took evolving insects on a non-stop flight to domination; [internet] [cited 2006 may 8]. Available from:
http://www.universityscience.ie/pages/scimat_evolving_insects.php
2. Wikipedia contributors. Insects [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 17, 05:19 [cited 2006 May 8]. Available from:http://en.wikipedia.org/wiki/Insects

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
0001
Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
My blog URL: http://mukwevholufuno.blogspot.com

HOW THE FIRST PLANTS AND ANIMALS EVOLVED AND BECAME DEPENDANT ON EACH OTHER.

During the period of Cenozoic era, "co-evolution between plants and animals species occur"(4). It has been profound that certain plants and insects influence another in evolution, in a process known as mutualism where all organisms benefit from each other. They firstly evolve in the aquatic environment before they evolve on land.

Species that co- evolve were single cell plant and multicelled eukaryote organism, "the blue-green algae was the single cell plant which evolve on the sea"(2). It was the first species to generate its own food in a process known as photosynthesis where sunlight and water are used; during this process oxygen is also generated. While animal cannot produce its own food," they depend direct or indirectly on plants for its survival, and for animal to be evolved on earth it is traced back to plant this show dependency of animal to plant". (2)

"The oxygen that the algae produce spread all over the aquatic environment, it began to fill the atmosphere and this made it possible for other organism to develop".(2) Because of high concentration of oxygen produced by algae in the atmosphere, it tends to give access to animal species to evolve on land. Oxygen form part of ozone layer in the upper atmosphere which tends to block the dangerous ultraviolet rays of the sun, these rays was making it impossible for organism to live out of water. But it was simple for plant to survive on land because they can utilise the ultra violet rays into food.

Simplicity of plant to convert sunlight into food made it possible for plant to evolve on land, and the first plant to evolve on land was Mosses. This made it possible for other animal to evolve on land, because of the oxygen generated by plant which forms the ozone layer that block the ultraviolet which restrict life of organisms to exist on land.

Mutualisation which has develop between plant and animal species during co evolution influenced by the resource that they need to survive on, during pollination plant depend on animal or insect.while insect or animals depend on plant for oxygen and plant depend on carbon dioxide which is released by organism as by product which is used to generate food in the process of photosynthesis. For each species to survive it have to depend on the other directly or indirectly. (4)

This dependency between plant and animal species can be seen during reproduction, where plant depends on organism to transfer pollen grains to the female flowers. This helps the plant to reproduce and increase plant population, which is simple method to transfer pollen than wind pollination which need quality seed to be dispersed. While organisms benefit from plant through food and habitant for reproduction that the plant provides, mostly this happens to insects such as moth and bees. (4)

Sometimes plant and organisms become total depend on each other, this happen when one insect only function to pollinate their pollen grains only and it find habitant on the same type of plant ‘s flower. Some become specific to that species only and they protect that species from herbivores. For example, species such as "Yucca (Plant) and Moth(organism) they depend on each other yucca provide habitant for moth and allows it to reproduce on its flower where its larvae (caterpillar) live in developing ovary and eat yucca seeds,(4) while moth function as the pollinator". (3)

"This mutualism can also be seen in the acacia trees and acacia ants, these ants are specifically depends on the acacia tree for foods. They tend to protect the acacia tree from the herbivores which feed on it and also prune the seeds of any plants that found under acacia tree. This ants sting the animal that feed on acacia or scratch on it, and the ants benefit from the substance that the acacia produce as a food". (4)

In conclusion, plants and organisms depend on each other in a process known as mutualism where all benefit. plant play a role in bring life on earth as the primary producer of factors that sustain life, while animals generate carbon dioxide that sustain plants and also increase the population of plants in the process of reproduction, organisms function as the pollinator.
All in all most of the species in the environment depend directly or indirectly to the other.

References:

1. Kazlev.A.M. 2002, Plants, (Land plants) [Internet] 2003 April 28 [cited 2006 May 08].Available from: http://www.palaeos.com/Plants/default.htm

2. Kohler, S. Plants, [Internet] 2006 May 8, 14:30. UTC [cited 2006 May 07]. Available from: http://www.blueplanetbiomes.org/plants.htm

3. Mrs.Ramsay.M. (et al).1995[internet]the Yucca Plant and the Yucca Moth.[cited 2006-May-08]Available from:http://www.emporia.edu/ksn/v41n2-june1995/introduction.htm

4.Mr.Carter J.S.1999.Coevolution and Pollination.[Internet]cited 2006-May-08]Available from:http://biology.clc.uc.edu/courses/bio303/coevolution.htm



Mr Elelwani Muanalo
NISL- Ecological Informatics Student
CSIR Pretoria
Tel: +27 12 841 2133
Fax: +27 12 842 7024.
Email: http://www.blogger.com/emuanalo@csir.co.za
My bloger URL: http://www.emuanalo.blogspot.com/

THE SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Insects use different signals to attract their mates. These include the use of pheromones, nibbling, waving of abdomen, sound and display of mating behaviour. Insects use odors to attract male from a distance. Majority of insects have contact sex pheromones on their cuticles that allow each sex to clearly identify the other once when they contact each other. Pheromones are usually used by social insects such as ant, termites and honeybees to differentiate nest mates and non nest mates.

In moth, the main determinant of female attractiveness is pheromone tilter. "A virgin female, biosynthesize pheromones and release them to attract males. After mating they cease synthesizing and releasing pheromones" (1). Pheromones biosynthesis in female moth is stimulated by a brain factor called pheromone biosynthesis activating neuropeptide. Male moths often trace a side to side crisscross flight way as they follow the windborne pheromones to its source. When the male arrives where there is a female, the physical contact is made. Mating proceeds almost instantaneously. However, in some moths upon his arrival a male releases his unique courtship pheromones and fans it over female with wings.

American cockroach (Periplanete Americana) begins when a mature female emits pheromones that attract male or many males on the mating ground. When the male accept this enticing signal, he approaches and flaps his wings to show his interest toward her. He will then probe the female with his abdomen as a way of searching for the origin of the omitted pheromones. Finally mating by males backing into the female and exchange sperm (2).

In some insects nibbling, waving of the abdomen and hissing are displays of mating behaviour. Some males will also emit sexual pheromones of their own initiate courtship and assume calling posture by exposing sexual gland of their abdomen called tergites. If the female is next to the male, she will open her genital atrium widely therefore exposing her atrium glands (2).

"Water striders or gerrids attract mates by using legs to create patterns of ripples on the surface of water" (2). Some insects use sound signals to attract mates. They also use the pattern of light flashes from firefly or chirps from a cricket are conspicuous signals used to attract mate. Cricket, grasshoppers as well as cicadas attract mating partners by sounds which produce the process of stridulation. Cicadas make their sound by clicking a taut membrane (4). Among grasshoppers and cricket, stridulation involves rubbing one body part against another to produce sound. Both males and female have a unique ears called tympana, for detecting the calls or songs from others.

"In Drosophila melanogaster, males are also attracted by pheromones of female and female movement. The amount of courtship a female elicit from males is used as a measure of her attractiveness. A virgin female are vigorously courted by whereas mated female elcit less courtship"(3). Some insects use antennae to hear sound made by other species members. For instance male mosquitoes use their featherlike antennae to hear sound of the female wing beats. Female insects become less attractive to male insects after mating.

Some female insects stop releasing pheromones after mating for examples Gypsy moth Lymantria dispar and brown-banded cockroach Supella longipalpa. However they rely on sperm to regulate their attractiveness. In contrast, Helicopverpa zea stop to release pheromones for only one night after mating. The process is accessory gland products that make up the spermatophore and not by sperm. Most of the insects use pheromones to attract mates.

References
1. Millar J (2002) Insect Chemical Ecology [Internet] 2006 May 06, 14:03 UTC [cited 2006 May 08] Avaliable from:
http://www.entomology.ucr.edu/events/winter2002.pdf

2. Randall T.N. Sexual Behavior Mechanisms in Cockroaches: How Have They Managed to Survive? [Internet] 2006 May 06, 13: 04 UTC [cited 2006 May 08] Available from: http://www.colostate.edu/Depts/Entology/courses/en507/papers-2001/ran%20dall.htm

3. Tram T & Wolfner M.F. Seminal fluid regulation of female sexual attractiveness in Drosophila melanogaster 2006 May 06, 09:30 UTC [cited 2006 May 08] Available from: http://www.pnas.org/cgi/content/abstract/95/7/4051
4. Wikepedia contributors. Insects and Behaviour, The free Encyclopedia[Online] 2006 May 07, 08:30 UTC [cited 2006 May 08] Available from:
Masiya Kedibone
CSIR PTA
0001
Cell No: 073 2519071
Tel No: 012 8412123
Fax: 012 842 3676
E-mail:kmasiya@csir.co.za
Weblog: http://kedibone-kedimasiya.blogspot.com/

THE DIVERSITY OF FLYING INSECT LIFE THAT HAS EVOLVED

Insects are small animals around us. They are regarded as invertebrate animals. They are grouped in the class Insecta. The insects are the largest and “most widely distributed taxon in the phylum Arthropoda” (3). They seem to be consisting of six legs and the three body parts. Their body parts are namely; the head, thorax and abdomen. Some of the insects are having one pair of wings, others are having two while some are having three pairs of wings (3).


Ancient types of insects were seen since the early dinosaur days. It seems as if these types of insects evolved for flying long time ago before some of the birds could fly. The class insecta is divided in to two subclasses, which are further divided into orders. The sub class Apterygota is divided into two orders, the microcoryphia known as “dragonflies, damselflies and the zygentoma known as silverfish, fibre brats” (3). These insects were known to be jumping insects, because they did not have wings. It seems as if they were indoors types of insects, spending much of their time under the sinks, bookshelves, etc (2).


The dragonflies and the damselflies are the insects of the subclass Apterygota. These insects evolved into the subclass zygentoma. According to the Insecta the insects in the sub class Apterygota are wingless. The lack of wings of these insects resulted as their disadvantage of being diverse. “After the insects gained the ability to explore more territory, they found new type of food which increased more species” (2). This resulted when they evolved the ability to fly. For example: the insects from the microcoryphia order evolved into the Odonato order (2).


The Odonato insects had about two pairs of wings. They were regarded as the best fliers. These insects were eating other insects caught on fight (1). The early flying insects seem to have expanded wings that stuck straight. It really shows that insects did not only develop for flight, in the past 300 million years ago, some of the insects had evolved folding wings. This modernism really gave the diversity of insect’s improvement. Those insects can keep their wings safely tucked away as “they move slowly through leaf litter, squeezed under tree bark or even dived into water” (3).


The evolution of insects became successful because of the plants. The insects depend on the plants for their survival. It seems as if plants play important role to insects, for example, by providing large amount of food for the insects. The insects evolved “defences against the sophisticated chemical weapons in plants”. There are some of the insects that are able to recycle the poisons from the plants, for example monarch butterflies (1).


Evolution happens every where, even in insects evolution took place. Some of the insects descended from other insects, for example fleas descend from mosquito. Fleas are just like the scorpion flies, “they have long wings and powerful eyes, aiding them in finding insect carcasses for food” (3). The boreids are known to be the flea’s closet relatives alive. The boreids seems to have the knowledge on how the scorpion flies evolved. “These 24 species walk across snow in late winter to feed on moss. Unlike other scorpion flies, snow fleas have tiny wings that are useless for flying. They don't have the keen eyesight of other scorpion flies, probably because they need their eyes only to detect predators” (3).



References:


[1]. [http://www.universityscience.ie/pages/scimat_evolving_insects.php, accessed on 07/05/2006: 09:00].


[2]. The family tree, [http://www.insecta.com/insecta/tree.htm, accessed on 06/05/2006, 12:00].

[3]. Wikipedia contributors. Insect [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 06, 12:59 UTC [cited 2006 May 23]. Available from: http://en.wikipedia.org/wiki/insects.



Ms Evelyn Maleka
CILLA CSIR
P.O. Box 395
Pretoria
0001
Tel: (012) 841 2133
Fax: 012 842 7024.
Email: emaleka@csir.co.za
http://malekaevelyn.blogspot.com/

THE SIGNAL USED BY INSECTS TO ATTRACT FOR SEXUAL REPRODUCTION


The sexual reproduction of insects occurs in different ways. They are male and females insects that mate and reproduce sexually. Sometimes there is shortage of males then some female’s species may reproduce. In a few species females produce only females. Most female’s insects have one or more spermatozoa where sperm can be stored and can be support by secretions from the spermsthecal glands. Female’s reproductive organ consists of ovaries, bilateral Oviducts, a common Oviduct and a vaginal.
The male reproductive systems consists of paired testes, where the sperm produced, seminal vesicles and is where sperm are stored,, accessory glands and a common ejaculatory duct. Mating is important for sexual reproduction. After mating, female’s insects from many species become less attractive.

Different insects used different sign to attract others. Some of these insects release glands called pheromones. However male hide a pheromone to make the female to mate. Intraspecific interaction species release Allelochemical. All these chemicals are called semi chemicals which are used for attraction.
Some insects used sound to mate but others used visions to mate. However females’ scorpion flies require a marriage gift of food from the male before mating. Then the males’ mates with her while she eats, because of these male are selected by the size and quality of gift. Further more those females can enjoy to mate with male. This is done by scorpion flies insects.

Insects used displays or dancing as a sign to attract females to mate. This is some of the strategies that are used by insects. Male fight or decide the winner by comparing size. Remember that the scorpion flies insects did not use this strategies. Some female insects not mate unless the male is in possession of a suitable territory or food source, These is done by other insects. Although female moths have smell glands on the abdomen . These chemicals attract males.


Vision is another strategy that is used by insects such as Butterflies. Butterflies are one of the important types of insects. One can said that, butterflies used colour and movement to attract male to mate. Because of these colours that are used by butterflies, then the males will follow coloured imitation by females.
Some male’s flies form dense group, when the females see that group, then they are attracted by the sight of these groups and they start to enter and select mate. Male fireflies as an examples are attracted “by, and fly to, the light beat produce by the wingless females” (2). I is said that both sexes of butterflies are meet on hill tops or other geographical outcropping and is where they will select a mate, but other insects form a group as I indicated above.

Mating strategies through sound. These are some of the strategies that are used mostly by mosquitoes one can know that mosquitoes are one of the important types of insects, and the male mosquitoes are attracted by the message produced by the wing vibration of the female. But some grasshoppers and cicadas are attracted by the sound produced by their males. Crickets use their burrows to resonate the sound, but cicadas use the enlarge empty space in their abdomens. Some leafhoppers communicate by using substrate vibration.
Males are allow to leave females after mating, giving those males opportunity to increase their reproductive success by locating and inseminating additional females. In many insects’ species, seminal fluid received from fluids during mating mediate post mating behavioural and physiological changes in females. http://www.ivyhall.district96.k12.il.us/4th/KKhp/1insects/buginfo.html

Just conclude, insects use sight, smell, sound, pheromones, nibbling and waving of abdomen as a strategies or sign to attract mate for sexual reproduction. When we talk about sound, we are referring to the noises that are made by insects. Species that do not use courtship, they use pheromones and Allelochemical as a strategies to attract males for mating.


References

1. Hoffmann, M.P. and Frodsham, A.C. 1993 Insect Facts and Information. [Online]. Available from:
http://www.ivyhall.district96.k12.il.us/4th/KKhp/1insects/buginfo.html[2006, May 08 13:11]

2. Knight,R. bcb Biodiversity Chapter 2. The swaming Horders [Cited 2006, May 08]. Available from:http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/page_40.htm

3. Nordlund, D,A, 1981. Semiochemicals their role in pest control. [Internet] [Cited 2006 May, 08]. Available from:http://ipmworld.umn.edu/chapters/flint.htm

Linette Netshiheni
CSIR
Pretoria
0001
Cell: 0820446442
Tell: 012 841 2133
Fax: 012 842 3676
tnetshiheni@csir.co.za
Weblog: http://tnetshiheni-linette.blogspot.com/

DESCRIBE HOW FIRST PLANT AND ANIMALS EVOLVED AND BECOME DEPENDENT ON EACH OTHER

Plants and animals are complex organisms. They have different kinds of cells. The scientists believe that there are more than 260.000 of plant species. Some plants are very short, they can be hardly seen. However, other plants are bigger than human or animals. In California, there is one of the biggest living plants on the earth that is called sequoia trees. Some stand more than two-hundreds and ninety feet (eighty eight meters) high and measure more than thirty feet (nine meters).

The first fossils were formed during the origin of life. These were the fossil of bacteria. The bacteria consist of single cell. After three and half billion years the first animal evolved. Bacteria used sunlight to manufacture their own food. These cells were prokaryotic meaning that they had no nucleus inside of the cell. Bacteria are still prokaryotic even nowadays. Three billion later the first animals evolved (kohler 2000).

It was earliest known multicellular eukaryotic animal fossil. These involved from “colonies” of single celled organisms. At this moment animals were small and simple (segmented worms, metazoans, coelenterates arthropods) finally evolve into all of the bigger and more multipart animals. At this moment, there was an unexpected “burst” of evolution, often called the Cambrian explosion. As results of explosion different type of invertebrates were involved in the ocean. The animals were consisted with hard shell which formed fossil after the death .These fossils include trilobites and brachiopods. At this moment the Oxygen in the atmosphere attained two percent. The first fish evolved (Kohler 2000).

The ozone layer was formed in the atmosphere due to high percentages of oxygen in the atmosphere. The ozone layer is essential because it blocks ultraviolet rays of the sun. It was nearly impossible for organisms to exist out of water because they would be killed by ultraviolet rays. As a result, it was possible for life form to involve on land. At this time, the ozone was sufficient to permit life on land. The earliest plants evolved. Plants existed on land before animals. The earliest plants were simple. The earliest plants were like the moss of nowadays.

Close to 2.5 billion years ago, the earth surface and atmosphere were stable enough to support primitive life. Single celled organisms started to develop in the seas that covered the planet. The blue algae appeared and across the seas. They used sunlight and water to manufacture their own food, during the process oxygen is created. As the blue-green grew on earth’s seas, they start to fill the atmosphere with oxygen. The oxygen which is produced by blue-green algae is used by other organisms to grow. This organism will produce carbon dioxide carbon dioxide, which algae needed to perform its functions (Kazlev 2000).

Plants are very much essential in the nature cycle. The oxygen that animals breathe comes from plants. Through the process of photosynthesis, plants take energy from the sun, carbon dioxide from the air, water as well as from the soil. As a result, they give off water and oxygen. Animals take part through respiration. The cycle of photosynthesis and respiration play an important role in sustaining the earth’s natural balance of oxygen, carbon dioxide and water.

Reference

1. Kazlev.A.M. 2002, PLANT,(land plants) [Internet] 2006 May o8, 11:00.UTC [Cited 2006 May 09, 10:12]. Available from:http://www.plalaeos.com/plant/default.htm
2.Kohler S (2000). Plants, [Internet] 2006 May 05, 10:40 UCT [cited 2006 May 09] Available from:
http://www.blueplanetbiomes.org/steppe_plant_page.htm
3.McLand, E. (2004). The quite Evolution of Trees. [Online]. Available from:http://www.ecology.com/feature-stories/quiet-evolution-of-trees/index.htm [cited 2006 May 09]

Masiya Kedibone
CSIR PTA
0001
Cell No: 073 2519071
Tel No: 012 8412123
Fax: 012 842 3676
E-mail:kmasiya@csir.co.za
Weblog: http://kedibone-kedimasiya.blogspot.com/





THE WATER VASCULAR SYSTEM THAT CHARACTERIZES ANIMALS THAT OCCUR IN THE PHYLUM ECHINODERMATA

Enchinodermata are phylum of marine animals found in the ocean at all depths. The echonodermata has six classes which are Asteroidea example starfish, Concentricycloipea example sea daises, Crinoidea example feather stars, Echonoidea example sea urchin, Holuthuroidea example sea cucumbers and Ophiuroidea example brittle stars. The phylum is containing approximately six thousands species and constitute the group of deuterostome invertebrates. Enchinodermata are characterizes by a unique vascular system.

The vascular system can be defined as a hydraulically controlled system consisting of a circumoral ring around the esophagus with connecting radial canals each leading to an ambulacrum. "The vascular system can be closed or opened. Crinoids have an open vascular system. The water vascular system is used by echinoderm such as sea stars and sea urchins. They may be evolved from tentacular system similar to those of deuterostone phyla such as tentacle pterebranch hemichordates"(1). However, there are different kinds of derived features of the vascular system, these include an embryological origin from left mesocoel, podia arranged along branches (ambulacra), and a central curcumesophagel ring (1).

The characteristics of vascular system do differ according to class. Crinoid has madreporite with multiple pores and madreporite may be replaced by minute scattered openings called hydropores. It has no polian vesicles, tube feet suckers and ampullae on podia. "Podia penetration is between plate and podia spacing is stumble . In asteroid madreporite of vascular system has aboral" (1). Some asteroid have tube feet sucker whereas others do not have. Podia penetration is between plates. It has ampullae on podia.

In Ophiuroid, madreporite of vascular system has oral. It has a polian vesicles Ophiuroid does not tube feet sucker. Podia penetrations are found between plates. Podia spacing is paired. It does not have ampullae on podia. In Echinoid madreporite has aboral. It has polian vesicles, tube feet sucker may be present or absent. "Podia penetration is paired through plates. Podia spacing is stagger. It has ampullae on podia. In Holothuroid madreporite are internal" (3). It has polian vesicles. Tube feet sucker a may be present or absent. Podia penetration between suckers may be present or absent. Podia penetrations are found between plates. Podia spacing is stagger. It has ampullae on podia (1).


Vascular systems network canals to create hydrostatic pressure, to help the starfish to move. Water enters through sieve plate or madreporite on aboral surface into a short stone canal. Stone canal connects to a circular canal around the mouth called the ring canal. "Five radial canals carry water to hundreds of paired tube feet. Bulb-like sacs or ampulla’s on the upper end of each tube foot contract and form suction to help move, attach or open bivalves’ mollusk shells and create suction to pull valves apart slightly" (3). Starfish exerts its stomach through its mouth and inserts into prey. Stomach secretes enzymes to partially digest bivalve then stomach withdrawn and digestion completed inside the starfish (1).

"The vascular systems perform different functions in echinoderm; these include locomotion, respiration, and feeding" (2). Most of the sensory neurons are located at the podia which are also part of this organ. Most oxygen enters starfish through diffusion into the tube feet. "This water vascular system can be used as a source of oxygen for respiration" (3). Many sea cucumbers also have a complex respiratory tree. The surface of many echinoderms is perforated by extensions of the body wall. Through these thin membranes of the body wall respiration can take place.

The vascular systems are very essential to echonodermata. They are responsible for digestion, locomotion and respiration. Even though echonodermata do differ with some characteristics but they all have vascular system. The vascular system is either open or close.

References

1.Denning D & Russell B. The Biology of Echinoderms [Internet] 2006 May 05, 12:30 UCT [cited 2006 May 07] Available from: http://ebiomedia.com/prod/BOechinoderms.html%202000-2005

2.Wikepedia Contributors. Water vascular system [Internet] Wikipedia, The free Encyclopedia, 2006 May 05, 11:15 UCT [Cited 2006 May 07] Available from: http://en.wikipedia.org/wiki/water vascular

3.Gregory A.W. Echinodermata. [Internet] 2006 May 05, 14:10 UCT Available from: http://tolweb.org/Echinodermata

Masiya Kedibone
CSIR Pretoria
0001
Cell No: 073 2519071
Tel No: 012 8412123
Fax: 012 842 3676
E-mail:kmasiya@csir.co.za
Weblog: http://kedibone-kedimasiya.blogspot.com/