Evolution

Question 1

Who was Lamarck?

Answer 1

Lamarck proposed one of the earliest theories of evolution.

Question 2

Describe Lamarck’s theory of evolution.

Answer 2

• Lamarck proposed that organisms could change over time due to changing environmental conditions.
• His theory proposed changes could occur within an organisms lifetime and be passed on to offspring.

Question 3

What was the power of the Darwin-Wallace theory of evolution by natural selection.

Answer 3

• identified a mechanism or cause of evolution.
• mechanism was testable by observation and experimentation.
• identified that individual organisms do not evolve in their life - but evolutionary changes occurs over many generations in populations.

Question 4

Describe the Darwin-Wallace theory of evolution by natural selection.

Answer 4

• Organisms produce more offspring than can survive.
• Offspring have variation, some variations are more suited to environments than others.
• Individuals with favourable characteristics are more likely to survive and reproduce.
• Successful generations will become modified over time - eventually becoming a new species.

Question 5

Define allele frequency.

Answer 5

How common an allele is in a population.

Question 6

Define gene pool.

Answer 6

The combination of different genes present in an interbreeding population.

Question 7

Define mutation.

Answer 7

A change in an organism that occurs when DNA is changed.

Question 8

Define natural selection.

Answer 8

The mechanism for evolution in which individuals with traits the best adapted to selection pressures in their environment survive and pass on their genes. Also known as ‘survival of the fittest’.

Question 9

Outline the steps of natural selection.

Answer 9

1. Variation - there is a variation in phenotypes between individuals in a population.
2. Selection Pressure - a specific selection pressure exists that causes a struggle for survival.
3. Adaptations - individuals with the advantageous phenotype overcome the selection pressure, survive and reproduce. Individuals with unfavourable phenotypes decrease in number.
4. Selection - organisms with the advantageous phenotype pass on their genes to the next generation. Successive generations will be genetically more like them and better adapted to the environment.

Question 10

Define speciation.

Answer 10

The process by which one species splits into two or more seperate species through evolutionary changes that can no longer produce fertile offspring.

Question 11

Describe the process of speciation.

Answer 11

1. Variation - there must be variation in the population.
2. Isolation - different groups are prevented from interbreeding, preventing gene flow.
3. Selection - natural selection affects the genotype and increasing frequency of mutations that prevent the groups breeding even if they got back together.

Question 12

Define genetic isolation.

Answer 12

Factors that prevent gene flow or mating between two populations.

Question 13

Identify types of genetic isolation.

Answer 13

• Geographical barrier - separation by physical barriers, e.g., mountains.
• Ecological - different niches.
• Temporal - different breeding cycles.
• Behavioural - different courtship behaviours.
• Structural - differences in reproductive organs.

Question 14

Define homologous structures.

Answer 14

Structures in organisms that have a similar structure and provide evidence of a recent evolutionary relationship.
- Similar structure
- Different function
- Closely related

Question 15

Define analogous structures.

Answer 15

Structures in organisms that perform a similar function but are structurally different, suggesting no recent common ancestor. Structures have been developed due to similar environments and selection pressures.
E.g. Butterfly and bat wings.

Question 16

Define divergent evolution.

Answer 16

Process by which two or more species evolve from a common ancestor, forming new species due to change in environment.
E.g., Finches on Galapagos Islands created different species due to different foods.

Question 17

Define convergent evolution.

Answer 17

Process by which two of more unrelated species adopt similar adaptations (analogous structures) in response to common environmental conditions.
E.g., Sharks and dolphins are similar in appearance but not related.

Question 18

Define fossils.

Answer 18

The preserved remains of ancient life.

Question 19

Define transitional fossils.

Answer 19

A fossil that shares characteristics of both its ancestral group and existing descendant group. ‘Missing link’ between related species.
E.g., archaeopteryx is the transitional fossil between velociraptors and chickens.

Question 20

Describe the process of fossilisation.

Answer 20

1. The remnants of an organism are covered in sediment.
2. Layers of sediment build up and pressure pushes these layers together forming sedimentary rock.
3. In the absence of oxygen, microorganisms and other disturbances, the remains are preserved.

Question 21

Conditions for fossilisation.

Answer 21

• conditions that reduce the rate of decomposition.
• areas of rapid sediment accumulation.
• constant cool temperatures.
• low light availability.
• protection from scavengers and decomposers.

Question 22

Describe fossil dating techniques.

Answer 22

• Absolute dating - determines an age (range) of a fossil using the breakdown of radioisotopes such as carbon-14.
• Relative dating - uses the position of fossils in strata (layers of sedimentary rocks) to indicate a fossils age in comparison to other fossils.

Question 23

Define biogeographical distribution.

Answer 23

• The study of how the continents move across Earth and how this directly affects the location of organisms.
• Continents now separated by oceans and containing identical fossil species were once connected in the past.

Question 24

Define vestigal structures.

Answer 24

• Structures and organs that have no apparent function and appear to be residual parts from a past ancestor.

Question 25

Define Embryology.

Answer 25

• The study of organisms in embryonic form.
• Embryo’s with similar anatomy share some of the same genes for the development of the embryo indicating recent shared ancestry.
• E.g human and turtle embryos both have the anatomy of gill slits.

Question 26

Define DNA sequencing.

Answer 26

• Analysis of DNA and genetic code for similarities.
• Species with similar DNA indicate a recent shared ancestor.

Question 27

Define protein structure.

Answer 27

• Compares similarities and differences of amino acid sequencing in proteins.
• Closely relates species have more similarities in amino acid sequence.

Question 28

Define selective breeding.

Answer 28

The process by which humans can select or remove particular traits from a population by directly controlling the breeding of animals or plants.

Question 29

Outline the requirements of selective breeding (artificial selection).

Answer 29

1. Variation - individuals in a population vary genetically, leading to phenotypic differences.
2. Selection pressure - Direct human intervention places an artificial selection pressure upon a population of individuals, allowing only certain individuals with desirable traits to breed together.
3. Heritability - selected trait must be heritable, allowing it to be passed on from parents to offspring. Therefore, after reproduction, the frequency of the selected allele increases.

Question 29

Compare selective breeding and natural selection.

Answer 29

• Selective breeding involves artificial selection pressures. Humans directly select desirable or remove traits from a population.
• Natural selection involves environmental selection pressures. Natural pressures, eg. predation, climate change, food availability, select individuals with advantageous traits.

Question 29

Define domestication.

Answer 29

The process of selective breeding to tame a species to be kept as pets or on a farm.

Question 30

Define living fossil.

Answer 30

Existing species descendant from ancient ancestors that have not changed in a very long time. Since selection pressures have not changed therefore there has been no pressure for the organism to change.

Question 31

Describe continental drift.

Answer 31

• The theory that continents were once part of a single landmass called Pangaea, which later split into multiple continents.
• Fossil and organism distribution supports continental drift.
• Continental drift explains the distribution of similar non-flying/swimming species separated by oceans.

Question 32

Define adaptation.

Answer 32

A characteristic that helps an organism survive and reproduce in its natural environment.