Speciation definitons

Question 1

Allopatric Speciation

Answer 1

Speciation occurs due to populations being GEOGRAPHICALLY SEPARATED.

Question 2

SUB 1 (ALLO) Selection pressures

Answer 2

In the different environments, there are different conditions (Give examples from context).
Why important?
-different alleles will be selected for and so frequencies of different alleles in the different populations will start to diverge.

Question 3

SUB 2 (ALLO) Mutations

Answer 3

Permanent change in the DNA of the organism (Must occur in gametic cells).
Why important?
-Different mutations occur in different populations. If beneficial mutations then these will increase in frequency.

Question 4

SUB 3 (ALLO) Reproductive Isolation Mechanisms (RIMS)

Answer 4

Due to different selection pressures and mutations, genetic differences will ACCUMULATE to the point of pre-zygotic or post-zygotic RIMS developing. ( Pre - occurs before mating, post - less common)
Why important?
- RIMS = NO GENE FLOW
-find examples from context (e.g. behavioural- singing/dancing, courtship, Temporal = time difference of mating, niche/habitat differentiation)

Question 5

Divergent Evolution / Adaptive radiation

Answer 5

-Genetic differences accumulate to the point of divergence where the two populations are reproductively isolated from each other.

Adaptive Radiation: A special type of divergence where ONE species diverges into many different species in a relatively SHORT period of time.

Evidence for both:
-Homologous structures ( e.g. pentadactyl limbs)

Adaptive Radiation and punctuated equilibrium associated with environmental change.

Question 6

Punctuated Equilibrium

Answer 6

Appearance of many species in a short period of time after a long period of stasis.

(Long period of stasis, sudden burst of species)

• example from context e.g. (20 species appear over 2 million years)

Question 7

WHEN mentioning ALLOPATRIC, see if you can talk about FOUNDER EFFECT.

Answer 7

-When a group from the original populations colonise a new area.

ALWAYS MENTION - This population is NOT representative of the original population in terms of its allele frequency and composition. AND is prone to GENETIC DRIFT.

Question 8

Sub 1 Genetic Drift (FOUNDER)

Answer 8

Change in ALLELE FREQUENCY in a population due to chance events - especially prevalent in small populations (like founder population).

As a result of Genetic Drift, this could lead to ALLELES becoming LOST of FIXED (Homozygous).

Question 9

Sympatric Speciation

Answer 9

Speciation that occurs within the SAME Geographical Area.

Why does it occur?
-Generally to REDUCE COMPETITION
- Occurs due to niche differentiation - find examples OR in plants POLYPLOIDY.

Condensed answer: Each niche = diff mutations and selection pressures = genetic differences to accumulate = NO GENE FLOW = RIMS develop further stopping gene flow.

Question 10

Sub 1 Selection Pressures (Symp)

Answer 10

In the diff niches there are diff conditions. - find examples from context.
- Different alleles will be selected for and so frequencies of different alleles in the different populations will start to DIVERGE.

Question 11

Sub 2 Mutation (Symp)

Answer 11

Permanent change in the DNA of the organism (Must occur in gametic cells).

Different mutations occur in different populations. If beneficial mutations then these will increase in frequency.

Question 12

Sub 3 RIMS (symp)

Answer 12

• Due to diff sel pressures and mutations genetic differences will accumulate to the point of pre or post-zygotic RIMS developing.
  RIMS = NO GENE FLOW - FInd examples)

Question 13

SYMP - PLANTS = Polyploidy

Answer 13

In plants - When a species chromosome set number is increasing e.g. 3n, 5n, 6n.

INSTANT SPECIATION: New species formed in one generation = involves an increasing no of chromosomes.

• OCCURS due to NON-DISJUNCTION (When chromosomes fail to separate during meiosis = diploid gamete) of chromosomes during cell division.
  -Leads to Instant Speciation as the resultant offspring have a different no of chromosomes than the parent species, (I.e reproductively separate).

Question 14

Autopolyploidy

Answer 14

Involves one species
- find examples and chromosome no. from context.

Question 15

Allopolyploidy

Answer 15

Involves 2 species
-find examples and chromosome no. from context.

Question 16

Symp = see if you can talk about Bottleneck EFFECT

Answer 16

• When a population is greatly reduced in numbers.
  ALWAYS MENTION:
• the resulting bottleneck population is no longer representative in terms of the allele composition and frequency.
• LEADs to genetic Drift
• Even if the population does recover in terms of number it is greatly reduced in terms fo genetic diversity.

Question 17

Convergent Evolution

Answer 17

Condense Answer- 2 species/populations start looking at the same/similar adaptations due to similar sel pressures = ANALOGOUS STRUCTURES.

• Animals that have similar adaptations to the environment (but different evolutionary origins) due to similar selection pressures.
• find examples from context- if cladogram- choose species that look similar but are as far as possible on the evolution tree. (e.g. Dolphin and Shark).

Question 18

Co-Evolution

Answer 18

When the evolution of one species affects the evolution of another.
- find examples on context - e.g. nectar feeding birds and flowers with long corolla.

Question 19

Gradualism

Answer 19

Rate of evolution that occurs at a slow and steady pace = non-changing environment = slow appearance of species.
- Associated with stable/ Not major environmental changes.

Question 20

Species

Answer 20

A group of organisms that can reproduce with one another in nature and produce fertile offspring.