Evolution 10.3 Gene Pools and speciation

Question 1

What is a gene pool?

Answer 1

consists of all the genes and their different alleles, present in an interbreeding population

Question 2

How can multiple gene pools exist?

Answer 2

populations of same species can be geographically isolated

Question 3

How can individuals contribute to the gene pool of the next generation?

Answer 3

reproduction

Question 4

What is genetic equilibrium?

Answer 4

when all members of a population have an equal chance of contributing to the future gene pool

Question 5

What is evolution?

Answer 5

the cumulative change in the heritable characteristics of a population overtime

Question 6

Why can evolution occur?

Answer 6

mutations like new alleles, selection pressures favouring the reproduction of some varieties over others, barriers to gene flow between different populations

Question 7

If a population is small, how can evolution additionally occur (cannot occur in large population)?

Answer 7

random events can also have a significant effect on allele frequency

Question 8

What are selection pressures?

Answer 8

environmental factor that act selectively on certain phenotypes resulting in natural selection

Question 9

What are the three patterns of natural selection?

Answer 9

stabilizing selection, disruptive selection, and directional selection

Question 10

What occurs during stabilizing selection?

Answer 10

Selection pressures act to remove extreme varieties.

Individuals with the average form of a trait have the highest fit.

Question 11

Give an example of stabilizing selection.

Answer 11

Human babies (too small ones are unable to defend themselves from infections and staying warm, too large ones are too large to deliver naturally)

Question 12

What occurs during disruptive selection?

Answer 12

Selection pressures act to remove intermediate varieties, favouring the extremes
Individuals with either extreme variation have a greater fitness than individuals with the average trait.

Question 13

What occurs during directional selection?

Answer 13

The population changes as one extreme of a range of variation is better adapted.
Individuals that display a more extreme form of a trait have a greater fit than individuals with an average form of the trait

Question 14

What is speciation?

Answer 14

formation of a new species by the splitting of an existing population. They become reproductively isolated

Question 15

When does speciation occur?

Answer 15

when various barriers isolate the gene pool of one population from tat of another.

Question 16

What are the types of reproductive isolation?

Answer 16

Temporal (sympatric), Behavioural (sympatric), Geographic (allopatric)

Question 17

What does reproductive isolation geographically mean?

Answer 17

Geographic separation of population where species come from same ancestor but because of different environmental pressures, need to adapt that causes them to evolve differently.

Question 18

What does reproductive isolation behaviourly mean?

Answer 18

Sometimes isolation of gene pools occurs within the same geographical area.

When closely related individuals differ in their courtship behaviour, they are often only successful in attracting members of their own population

Question 19

What does reproductive isolation temporarily mean?

Answer 19

For temporal isolation of gene pools in the same area, Populations may mate or flower at different season or different times of the day

Question 20

In what ways can speciation occur?

Answer 20

abruptly or gradually due to divergence of isolated propulations

Question 21

What is gradualism?

Answer 21

idea that species slowly change through a series of intermediate forms. Evolution occurred through long sequence of continuous intermediate forms

Question 22

Why could gradualism not be completely true?

Answer 22

there was sometimes an absence of intermediate form in fossil records

Question 23

What is punctuated equilibrium?

Answer 23

Long periods of relative stability in a species are “punctuated” by periods of rapid evolution

Question 24

How could gaps in fossil record possibly not be gaps at all?

Answer 24

Punctuated equilibrium reasons that there was not no long sequence of intermediates.

Question 25

What can lead to rapid speciation?

Answer 25

geographical isolation (allopatric speciation), opening of new niches within a shared geographic range

Question 26

Where is rapid speciation common?

Answer 26

organisms with short generation times (prokaryotes/insects)

Question 27

What are polyloid organisms?

Answer 27

more than two sets of homologous chromosomes

Question 28

How do polyloids happen?

Answer 28

• Hyberdization event between different species
  
  • Occurs when chromosomes duplicate in preparation for meiosis but then meiosis does not occur
  • The result is a diploid gamete that when fused with a haploid gamete produces a fertile offspring.
  • It has become reproductively isolated from the original population
  • It can self -pollinate or mate with other polyploidy plants
  • Can lead to sympatric speciation

Question 29

Describe characteristics of polyploid?

Answer 29

polyploids may be well adapted to their environment;
common in plants / named example of speciation by polyploidy;
polyploidy is a form of sympatric speciation;
leading to reproductive isolation from parent species;
polyploid individuals can interbreed with one another;
A. named example (eg tomato, wheat, sugar beet, bagworm moth);
B. alteration of number of chromosomes (euploidy) / three (or more) sets of chromosomes;
C. larger nuclei / larger cells;
D. larger organisms / more vigorous; E. (generally) infertile;
F. alloploidy when of different species;

Question 30

Outline example of a speciation through polyploidy

Answer 30

Alliun genus (onions, garlic and chives);
Determining species in the genus presents challenge to taxonomist as polyploidy are common within genus;
results in reproductive isolation (otherwise similar population)
reproduce asexually, polyploid gives advantage over diploidy under selection pressure;

Question 31

What is an endemic species?

Answer 31

A geographically isolated species

Question 32

What is the difference between analogous structures and homologous structures?

Answer 32

• homologous traits derive from common ancestors

- analogous traits developed from convergent evolution

Question 33

What type of evidence is used to make a cladogram?

Answer 33

• DNA sequence
• amino acid sequence
• mitochondrial/chloroplast DNA
• shared characteristics

Question 34

Why should a cladogram be constructed with more than one type of evidence?

Answer 34

• higher degree of certainty

- some could be misleading/anomalies

Question 35

Why is mitochondrial DNA used to develop cladograms based on molecular clocks?

Answer 35

• Mitochondrial DNA sequences of genes are short, easy to examine
• mutations accumulate over time
• divergence is represented by amount of difference
• the greater the difference the earlier the divergence

Question 36

Explain how mutations can be used as molecular clocks

Answer 36

• DNA base sequence/amino acid sequence differences result from mutations
• accumulate gradually over time
• constant rate is seen as molecular clock
• number of difference in sequence correlate to the time since species diverged from common ancester