5.1 Evidence for Evolution

Question 1

define evolution and name people who are opposed to it

Answer 1

this is the process by which hertiable characteristics of a species change over time as a result of natural selection

• people often oppose it for religious reasons

Question 2

how to fossils provide evidence for evolution

Answer 2

fossils have been found in various layers or strata of rock where they were deposited during different geological eras and we can use radioisotopes to identify teh exact age of the rocks and the fossils therefore

the study of these rocks is paleontology

1. the seqeunce of fossiles matches the sequence we would expect from evolution ( bacteria and finally land vertebrate which bony fish first and then placental mammals last)
2. the sequence also fits in with ecology groups and their interactions (plants before animals, land plants before land animasl etc)
3. known sequences of fossils have been found to ink together existing orgnaisms with their likely ancestors (horses and zebras are related ot the rhinoceros and the fossils link them to the Hyacotherium which is similar to a rhinoceros)

Question 3

how does selective breeding provide evidence for evolution

Answer 3

Humans have deliberately bred together specific organisms to produce offspring with desirable characteristics - artificial selection or selective breeding.

There is variation between these modern breeds of organisms that humans have helped to develop and the wild species

It is clear that the characteristics in these modern breeds have developed over a relatively short period of time due to artificial selection by humans

Therefore, the results of artificial selection are evidence that the natural changes in the characteristics of a species (i.e. evolution) are due to selection as well; the only difference being that evolution involves natural selection (without human input) and the changes occur over million of years.

Question 4

what are analogous structures and waht kind of evolution do they show

Answer 4

These are structures taht are superficially similar but actually very different e.g. fish and wale tail fins.

They arise die to convergent evolution

• different genetic origins
• superficially similar structure
• same function as similar environment

Question 5

what are homologous structures and how do they arise and give evidence for evolution

Answer 5

homologous structure are the opposite of analogous structures. They appear superficially different and and may perform different functions in different organisms.

e.g. the underlying structure of pentadactyl 5 digit limb of different vertebrates has similar bones

these adaptive radiation

• they have the same genetic origins
• but look different due to different environments to perform different functions

homologous structures which have the same underlying strucutre –> unity of type

–> evidence of evolution as there is no other reason for teh structure to have the same underlyign structure despite different functions, unless they have a common ancestor

also vestigial organs (e..g the appendix) are being slowly lost from organisms and are also explained by evolution as they no longer have a function

Question 6

what is speciation and where does it often occur

Answer 6

if 2 populations of the same species become seperated form each otehr so they cannot interbreed - the different environment wiull cause natural selection to act differently on seperate population

this will cause them to evolve in different ways to gain different characteristsc and eventually become two seperate species so that they cannot interbreed

this often occurs when organisms migrate to islands and become isolated from teh original population –> e.g. the galapagos islands finches

• different environementla pressures due to differenent food sources
• this means natural selection cuases different characteristics e.g. different beaks
• eventually a new species

Question 7

how does variation lead to evidence for evolution

Answer 7

• population are gradually evolving over time and slowly become seperate species adn it is difficult to identiy the point at which 2 populations are different

there can be a lot of variation between the population but are still teh same species

this large variation is beacuse teh same species have characteristics that are continually changing this is the evidence of evolution as it does not match the idea that species were created as distinict types of organsims that are unchanging