This website uses cookies to ensure you have the best experience. Learn more

The Evolution Of Animals Essay

5696 words - 23 pages

The Evolution of Animals

Eukaryotes come in two grades of organization: single-celled (protists) and multicellular (plants, animals, and fungi). The world today is full of complex multicellular plants and animals: how, why, and when did they evolve from protists?

Proterozoic Protists
A single-celled eukaryote or protist can carry chlorophyll (it can be an autotrophic, photosynthetic, "alga"), it can eat other organisms (it can be an organotrophic, "protozoan" "animal"), or it may do both.
Beginning about 1850 Ma, we find acritarchs, spherical microfossils with thick and complex organic walls. They are probably dinoflagellates that spent most of their life floating in the plankton.

We know that a very diverse array of plankton existed by 800 Ma, because they are known as fossils. But many amoebalike protists do not have cell walls made of cellulose and so do not preserve well. It's possible that while the surface layers of Proterozoic oceans had huge numbers of floating plankton, Proterozoic seafloors were crawling with successful populations of protists consuming the rich food supplies available in bacterial mats.

Evolving Metazoans from Protists: Anatomy and Ecology
A flagellate protist is a single cell with a lashing filament, a flagellum (plural, flagella), that moves it through the water. A sponge is the simplest multicellular variation on this theme. It contains many similar flagellated cells arranged so that they generate and direct water currents efficiently. Sponges are more advanced than simple colonies of choanoflagellates because they also have specialized sets of cells to form a body wall, to digest and distribute the food they collect, and to construct a stiffening skeletal framework of organic or mineral protein that allows them to become large without collapsing into a heap of jelly. Sponges are thus metazoan animals, not protists. Metazoans are not just multicellular, they have different kinds of cells that perform different functions.
Metazoans are most likely a clade, that is, they all descended from one kind of protist. All metazoans originally had one cilium or flagellum per cell, for example. Metazoans also share the same kind of early development. They form into infolded balls of internal cells which are often free to move, and are covered by outer sheets of cells that form an external coating for the animal: a skin, if you like.

The first metazoans were soft-bodied, and we have no fossil record of them. But we can look at the tremendous variety of living animals and at the geologic record to try to reason out what the first metazoans might have looked like and what they might have done.

There are only three basic kinds of metazoans: sponges, cnidarians, and worms. One can imagine scenarios for the divergence of the three great metazoan groups. All of them solved the problem of developing to larger size and complexity, but in different ways.

Sponges evolved by extending the choanoflagellate...

Find Another Essay On The Evolution of Animals

The Mistreatment of Circus Animals Essay

1844 words - 8 pages an end, a trainer arrives with a bull hook and thrusts it into the elephant’s side. Bloody wounds are all over its body from the mistreatment of the circus industry. This is the life that circus animals live each and every day. The animals are mistreated on a routine basis and are crammed into small boxcars for more than three-fourths of their life, serving the public for a moment of entertainment each night. The life of a circus animal is one of

The Unethical Treatment of Animals Essay

1870 words - 7 pages “Man is the highest rated animal, at least among all the animals who returned the questionnaire (Brault, 2009).” For years humans have been using animals for experimentation, food, clothing, sport and entertainment, manual labor, and let us not forget man’s best friend. The unethical treatment of animals can best be resolved by deontology contrasted with ethical egoism. Being human indicates the feeling of pain, pleasure, fear, and love; if

The Cloning of Livestock Animals

643 words - 3 pages behind the cloning of animals is high quality, healthy livestock, and to continue the genetics of many remarkable animals. Many supporters are talking about the possible benefits cloning could have on endangered species. The variability among living organisms, also known as biodiversity, is the safety of the wild and livestock population against the spread of diseases. Cloning is an attempt to keep one set of genes that are desirable by a purchaser

The Ethical Treatment of Animals

736 words - 3 pages I believe in the ethical treatment for all animals is an ethical obligation by all humans. We have come to an era that we believe that all humans should be treated equally and fairly. Well, what about our other living, breathing counterparts? They deserve to live their life as they choose in quality and in the pursuit of happiness. Just as Europeans came and took over Northern America's land and resources on the Indians. We have also taken

The Evolution of Sex

2520 words - 10 pages individual organism is part of an elaborate device that ensures the survival and replication of genes with the least possible biochemical alteration. Being that reproduction is thought to be one of the primary reasons for existence for many species, it is important to investigate its role in the evolution of sex. Webster defines reproduction as the act or process by which plants and animals give rise to offspring and which fundamentally consists

The Theory Of Evolution

1282 words - 5 pages basically C,H,O All have DNA and/or RNA for genetic codes All have similar Cell membrane structure All release energy by chemical respiration (except chemosynthetic bacteria) Jean- Baptiste Lamark lived from 1744 until 1829 and was a scientist from France. His ideas were the start of scientists thinking about evolution .He thought that animals and plants adapted to their changing surroundings in their lifetime and then passed on these

The Evolution of Whales

1131 words - 5 pages The Evolution of Whales The origin of modern day whales, a mystery that has puzzled paleontologists for years, may have just been solved with the discovery of an ankle bone. This discovery might sound simple and unimportant, but the bones of these ancient animals hold many unanswered questions and provide solid proof of origin and behavior. The relationship between whales and other animals has proven to be difficult because whales are

The Theory of Evolution

3076 words - 12 pages Bad grade because there are no citations Needs citations,overall very interestingBODYINTRODUCTION TO EVOLUTIONWhat is Evolution? Evolution is the process by which all living thingshave developed from primitive organisms through changes occurring overbillions of years, a process that includes all animals and plants. Exactly howevolution occurs is still a matter of debate, but there are many differenttheories and that it occurs is a scientific

The Evolution of Man

1859 words - 7 pages evolution. With the open environment, these creatures no longer climbed trees, but began walking, much in the fashion that we do today, over vast areas of land. They moved from one placee to the other in search of whatever they could dig up from the ground. However, it was supplemented by scavenged meat from carcasses, as well as small animals. We can notice that the physical appearance of these early human relatives is somewhat distinct

The Process of Evolution

1375 words - 6 pages Without evolution, and the constant ever changing environment, the complexity of living organisms would not be as it is. Evolution is defined as a process that results in heritable changes in a population spread over many generations (8).Scientists believe in the theory of evolution. This belief is based on scientific evidence that corroborates the theory of evolution. In Figure 1 the pictures of the skulls depict the sequence of the evolution

The Evolution of Communication

736 words - 3 pages The Evolution of Communication Since the earliest of years, communication has been an important part of life. The term communication is defined as a means to give or interchange thoughts, feelings, information, or the like, by writing, speaking, gesturing, etcetera ( Stein, 298). Communication allows humans and other life-forms to interact with each other and transfer important information. The information transferred could be comprised of

Similar Essays

Darwin's Theory Of Natural Selection And The Evolution Of Animals

953 words - 4 pages around them (eg. Bigger jaws for eating whole animals)giving the individual a quick advantage increasing reproductive success. A behaviour which will give an individual a competitive edge will likely lead them to a rapid evolution (eg. A strong male who wins all his competitions will have the right to impregnate the female allowing his genes to be perpetuated). A behaviour that is used with respect to other members of

The Evolution Of Evolution Essay

1419 words - 6 pages The views of society towards the creation of humanity have rapidly changed since the discovery of evolution. Nevertheless, there was a time before the world did not know the theory of evolution and the theories demonstrated by Sir Charles Darwin. Before the evolution, there were people who were subjected to religious ideologies of how mankind was created, they believed that the upper class was known to be “divine creatures”. However, the

The Military Use Of Animals Essay

1185 words - 5 pages From the earliest days of man, creative uses for animals have arisen. Since the time of them Mongolian chief Timur and Sultan Muhmad Khan, many military uses have been created. These creative ideas are still created today, now modern day countries find many uses of animals such as monkeys, seals, dolphins, goats, elephants, and other animals in the military. Though the truth is right in front of our eyes, many people do not believe that these

The Mistreatment Of Circus Animals Essay

1951 words - 8 pages reached the grand finale and has finally come to an end, a trainer swiftly arrives with a pointy bull hook and forcefully thrusts it into the elephant’s scarred side. Bloody wounds are all over its body from the mistreatment of the circus industry and trainers. This is the life that circus animals live each and every day. The animals are mistreated on a routine basis and are crammed into small boxcars for more than three-fourths of their life