Biology Edexcel Topic 4 (Evolution)

4.1B to 4.6B

What is evolution

A gradual change in the inherited traits within a population over time which occurs due to natural selection

Outline the theory of natural selection

1. Genetic variation exists due to mutations
2. This mutation gives the organism an advantage over the selection pressures (e.g. competition and disease)
3. Organism is better adapted to the environment and survives
4. Organism can reproduce, which passes on its beneficial alleles
5. Frequency of these beneficial alleles increases throughout the population

Why does competition between organisms in a habitat exist

The resources within a habitat that are required for survival are limited

Give some examples of competition between organisms within a habitat

Competition between animals for food or shelter, and competition between plants for light or water

Describe how antibiotic resistance UV bacteria can be used as an example to illustrate the process of evolution

1. Genetic variation exists due to mutations
2. Mutation gives bacterium resistance to a selection pressure (in this case it is antibiotics)
3. If an antibiotic is administered, the bacterium will be better adapted and survive while others won't
4. The bacterium can reproduce, passing on its resistant allele
5. Frequency of the antibiotic resistant allele increases throughout the population

Why is the development of antibiotic resistance in bacteria a good study for evolution

Bacteria reproduce very rapidly which allows for first hand evolution of evolution

How can the observation of fossils provide evidence for evolution

Older fossils contain simpler organisms whereas newer fossils contain more complex organisms, so competitive of fossils can be made to show that simple organisms evolved into more complex ones - fossils can also be organised chronologically which allows the changes in organisms over time to be observed

Describe the role of Darwin in the development of the theory of evolution by natural selection

He studied a variety of organisms whilst travelling the world in the HMS beagle and noted that traits could be passed from parents to offspring so proposed the idea of survival of the first and established the theory of natural selection, publishing his ideas in his book 'On the origin of species'

Describe the role of Wallace in the development of the theory of evolution by natural selection

He proposed a theory of natural selection that was similar to Darwin's though the mechanisms were different, and he gathered more evidence (e.g. studying the warning colourisation in butterflies) to support the theory

How has the theory of evolution by natural selection impacted modern biology and society

It enables the classification of organisms, influences modern medicine by emphasising the importance of finishing antibiotic treatments and the need for constant production of new antibiotics, and highlights the importance of high genetic diversity in habitats which aids conservation projects

What fossils have provided evidence for human evolution

Ardi - 4.4 million years old, Lucy - 3.2 million years old, and Turkana Boy (Leakey's discovery) - 1.6 million years old

What clues does Ardi give scientists about human evolution

She showed phenotypic traits which encompass characteristics of both humans and apes, such as having long arms and extended toes which are ape like characteristics, and the structure of her bones suggests she walked upright which is a human like characteristic

What clues does Lucy give scientists about human evolution

She shows phenotypic traits which were more human like than that of Ardi, such as the structure of her bones being more adapted to walking than climbing and having no extended toe, but her brain size was still closer to that of an ape's

What clues does Turkana Boy give scientists about human evolution

He showed traits comparable to that of modern day humans such as having a smaller brain size and arms that were much closer to the length of a human's

Why is fossil evidence valuable when examining human evolution

Fossils can be dated to know their age and a comparison of fossils can indicate how humans have changed over time

How has the development of stone tools provided evidence for evolution

There is a correlation between the development of more complex tools and an increase in brain size - probiotics tools are older than more complex tools and brain size has increased over time so as brain size increased (it has evolved), advancements in tool complexity were made

Describe methods used by scientists to date tools

Carbon 14 dating - estimating the age of carbon containing material that is found alongside tools (e.g. fur), and stratigraphy - using the age of the layers of sediment surrounding the tool as an indication of the age of the tool

What is a pentadactyl limb

A limb with five digits present in animals, birds, reptiles and amphibians

How does the pentadactyl limb provide evidence for evolution

The presence of the pentadactyl limb suggests that all species which possess it descended from a common ancestor as it is unlikely that they will have all developed that specific structure instead of developing a structure more suited for the purpose of the limb