Evolution

Question 1

What is evolution

Answer 1

gradual change in inherited traits (change in gene frequencies) in a population.

Question 2

What is micro-evolution

Answer 2

the small-scale changes in gene pools.

Question 3

What is Macroevolution

Answer 3

large scale changes in form.

Question 4

List evidence of evolution

Answer 4

fossils
comparative anatomy/embryology
comparative biochemistry

Question 5

What are fossils

Answer 5

any preserved part or impression of a dead organism

Question 6

How are fossils best preserved

Answer 6

Rapid burial in mud sedimentary rock, anaerobic - slows decay & no scavenging.
alkaline soil (acids dissolve bone).
mineral-rich hard parts (bones,
teeth) may remain.
Soft parts may be mineralised (organic matter replaced by minerals) – may occur in wet acidic anaerobic soil eg peat bog petrified wood.

Question 7

Explain why fossils are important

Answer 7

Shows change over time eg change in size. Many stay the same (living fossils).
Modern species can be traced through fossil relatives to distant origins.
Fossil species are often similar to, but a bit different from, today’s species.

Question 8

Explain comparative anatomy

Answer 8

where the body structure are similar in the same types of organisms.
Similarities in structure often suggest a species may share a common ancestor.

Question 9

Explain homologous structures

Answer 9

structures that are similar due to common ancestors on the evolutionary tree
eg pentadactyl
(5 digit) limb found in most vertebrates has the same basic structure.
Homology infers common ancestry followed by modification.

Question 10

what is analogous structures

Answer 10

Structures that have the same function in different organisms may come from quite different origins. Analogous structures do
 not imply an evolutionary relationship, but may
 indicate convergence

Question 11

What are vestigial organs

Answer 11

degenerate structures that no longer perform the same function as in other organisms.
must have been important in some ancestral form, but became redundant in later species.

Question 12

What is Comparative Biochemistry

Answer 12

Compare DNA or protein sequences - shows how similar they are => common ancestor.
Biochemical similarity is greatest among the most closely related species and smallest among the most remote.

Question 13

What is natural selection

Answer 13

the process where individuals with certain inheritable traits survive and reproduce more successfully than others, leading to evolutionary change in the population

Question 14

Explain what are the mechanisms of natural selection

Answer 14

Variation- includes Mutation, Random assortment of chromosomes in meiosis I, Crossing over in Meiosis, Random mating, Random fertilisation, Migration

Isolation - (Allopatric) Split into new habitats with new environments or reproductive barriers

Natural selection - favours the best suited phenotype. Variations inherited. Increased survival, more offspring, more % alleles into next generation.

Speciation - The 2 populations are no longer able to breed. Reproductive isolation

Question 15

What is the bottleneck effect

Answer 15

when a catastrophic event or period drastically reduces the size of a population

Question 16

What is the founder effect

Answer 16

a type of gene flow that occurs when a few individuals that have become isolated from a larger population do not carry all the alleles that were present in the original population

Question 17

Explain gene flow

Answer 17

The transfer of alleles that results from emigration and immigration of individuals between populations

Question 18

Explain genetic drift

Answer 18

a change in the gene pool of a population as a result of chance; usually occurs in small populations

Question 19

What are the mechanisms of speciation

Answer 19

Reproductive isolating mechanisms
Pre-reproductive
Post-reproductive

Question 20

Explain Pre-reproductive isolating mechanisms

Answer 20

a mechanism that prevents organisms from being able to interact to reproduce:
Geographic - separated by geographic features
Temporal - breed during different seasons
behavioural - different courtship patterns
morphological - different reproductive structures

Question 21

Explain Post-reproductive isolating mechanisms

Answer 21

a mechanism that prevents fertilisation occurring or an embryo developing into viable offspring if fertilisation does occur:
Gamete mortality - gametes do not survive
Zygote mortality - zygote forms but doesn’t survive
Hybrid sterility - offspring form but are infertile

Question 22

What is allopatric speciation

Answer 22

speciation that occurs due to physical or geographic isolation

Question 23

what is sympatric speciation

Answer 23

speciation that occurs without physical or geographic isolation