Adaptations?

Question

7.Explain how dna can provide some ievidence of evolution

8. Describe three exaples of direct evidence for evolution.

9.Describe at least three kinds of evildence that suggests that all primates might have shared a common ancestor.

10. what is the importances of Australopithecus

Answer 1

Biological evolution is genetic change in a population from one generation to another.  The speed and direction of change is variable with different species lines and at different times.  Continuous evolution over many generations can result in the development of new varieties and species.  Likewise, failure to evolve in response to environmental changes can, and often does, lead to extinction.

The evidence for evolution has primarily come from four sources:

1.     the fossil record of change in earlier species

2. the chemical and anatomical similarities of related life forms

3. the geographic distribution of related species

4.   the recorded genetic changes in living organisms over many generations

The Fossil Record

  

Geological strata containing an

evolutionary sequence of fossils

Remains of animals and plants found in sedimentary  rock deposits give us an indisputable record of past changes through time.  This evidence attests to the fact that there has been a tremendous variety of living things.  Some extinct species had traits that were transitional between major groups of organisms.  Their existence confirms that species are not fixed but can evolve into other species over time.

The evidence also shows that what have appeared to be gaps in the fossil record are due to incomplete data collection.  The more that we learn about the evolution of specific species lines, the more that these so-called gaps or "missing links in the chain of evolution" are filled with transitional fossil specimens.

                             Chemical and Anatomical Similarities

Living things on earth are fundamentally similar in the way that their basic anatomical structures develop and in their chemical compositions.  No matter whether they are simple single celled protozoa  or highly complex organisms with billions of cells, they all begin as single cells that reproduce themselves by similar division processes.  After a limited life span, they also all grow old and die.

All living things on earth share the ability to create complex molecules out of carbon and a few other elements.  In fact, 99% of the proteins, carbohydrates, fats, and other molecules of living things are made from only 6 of the 92 most common elements.  This is not a mere coincidence.

All plants and animals receive their specific characteristics from their parents by inheriting particular combinations of genes.  Molecular biologists have discovered that genes are, in fact, segments of DNA  molecules in our cells.

All of the tens of thousands of types of proteins in living things are made of only 20 kinds of amino acids.  Despite the great diversity of life on our planet, the simple language of the DNA code is the same for all living things.  This is evidence of the fundamental molecular unity of life.

      

Human arm bones

(typical vertebrate pattern)



In addition to molecular similarities, most living things are alike in that they either get the energy needed for growth, repair, and reproduction directly from sunlight, by photosynthesis , or they get it indirectly by consuming green plants and other organisms that eat plants.

Many groups of species share the same types of body structures because they inherited them from a common ancestor that had them.  This is the case with the vertebrates , which are the animals that have internal skeletons.  The arms of humans, the forelegs of dogs and cats, the wings of birds, and the flippers of whales and seals all have the same types of bones (humerus, radius, and ulna) because they have retained these traits of their shared common ancient vertebrate ancestor.

All of these major chemical and anatomical similarities between living things can be most logically accounted for by assuming that they either share a common ancestry or they came into existence as a result of similar natural processes.  These facts make it difficult to accept a theory of special and independent creation of different species.

Geographic Distribution of Related Species

Another clue to patterns of past evolution is found in the natural geographic distribution of related species.  It is clear that major isolated land areas and island groups often evolved their own distinct plant and animal communities.  For instance, before humans arrived 60-40,000 years ago, Australia had more than 100 species of kangaroos, koalas, and other marsupials  but none of the more advanced terrestrial placental mammals  such as dogs, cats, bears, horses.  Land mammals were entirely absent from the even more isolated islands that make up Hawaii and New Zealand.  Each of these places had a great number of plant, insect, and bird species that were found nowhere else in the world.  The most likely explanation for the existence of Australia's, New Zealand's, and Hawaii's mostly unique biotic environments is that the life forms in these areas have been evolving in isolation from the rest of the world for millions of years.

Genetic Changes Over Generations

The earth's environments are constantly changing, usually in subtle and complex ways.  When the changes are so great as to go beyond what most members of a population of organisms can tolerate, widespread death occurs.  As Charles Darwin observed, however, not all individuals always perish.  Fortunately, natural populations have genetic diversity.  Those individuals whose characteristics allow them to survive an environmental crisis likely will be the only ones able to reproduce.   Subsequently, their traits will be more common in the next generation--evolution of the population will have occurred.

This process of natural selection resulting in evolution can be easily demonstrated over a 24 hour period in a laboratory Petri dish of bacteria living in a nutrient medium.  When a lethal dose of antibiotic is added, there will be a mass die-off.  However, a few of the bacteria usually are immune and survive.  The next generation is mostly immune because they have inherited immunity from the survivors.  That is the case with the purple bacteria in the Petri dishes shown below--the bacteria population has evolved

This same phenomenon of bacteria evolution speeded up by human actions occurs in our own bodies at times when an antibiotic drug is unable to completely eliminate a bacterial infection.  That is the reason that medical doctors are sometimes hesitant to recommend an antibiotic for their patients and insist that the full dosage be used even if the symptoms of illness go away.  They do not want to allow any potentially antibiotic resistant bacteria to survive

try there sites:

bioweb.cs.earlham.edu/9-12/evolution/H...

www.gate.net/~rwms/EvoEvidence.html -

evolution.berkeley.edu/evolibrary/sear... - 9k

The genus Australopithecus (Latin australis "of the south", Greek pithekos "ape") is a group of extinct hominids, the gracile australopithecines, closely related to humans.

The fossil record seems to indicate that Australopithecus is the common ancestor of the distinct group of hominids, now called Paranthropus (the "robust australopithecines"), and most likely the genus Homo which includes modern humans. Although the intelligence of these early hominids was likely no more sophisticated than modern apes, the bipedal stature is the key evidence which distinguishes the group from previous primates who are quadrupeds. The morphology of Australopithecus upsets what scientists previously believed, namely, that large brains preceded bipedalism. If A. afarensis was the definite hominid which left the footprints at Laetoli, it strengthens the notion that A. afarensis had a small brain but was a biped. Fossil evidence such as this has made it clear that bipedalism far predated large brains. However, it remains a matter of controversy how bipedalism first evolved millions of years ago (several concepts are still being studied). The advantages of bipedalism allowed hands to be free for grasping objects (e.g. carrying food and young), and allowed the eyes to look over tall grasses for possible food sources or predators. However, many anthropologists argue that these advantages were not large enough to cause bipedalism.

A recent study of primate evolution and morphology noted that all apes, both modern and fossil, show skeletal adaptations to upright posture of the trunk, and that fossils such as Orrorin tugenensis indicate bipedalism around 6 million years ago, around the time of the split between humans and chimpanzees indicated by genetic studies. This suggested that upright, straight-legged walking originally evolved as an adaptation to tree-dwelling. Studies of modern orangutans in Sumatra showed that these apes use four legs when walking on large stable branches, swing underneath slightly smaller branches, but are bipedal and keep their legs very straight when walking on multiple small flexible branches under 4 cm. diameter, while also using their arms for balance and additional support. This enables them to get nearer to the edge of the tree canopy to get fruit or cross to another tree. Climate changes around 11 to 12 million years ago affected forests in East and Central Africa so that there were periods when openings prevented travel through the tree canopy, and at these times ancestral hominids could have adapted the upright walking behaviour for ground travel. It is suggested that the ancestors of gorillas and chimpanzees became more specialised in climbing vertical tree trunks or lianas, using a bent hip and bent knee posture which matches the knuckle-walking posture they use for ground travel. Humans are closely related to these apes, and share features including wrist bones apparently strengthened for knuckle walking.[2][3]

Radical changes in morphology took place before gracile australopithecines evolved; the pelvis structure and feet ar