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Biology 2-Exam 1 > Evolution > Flashcards

Evolution Flashcards

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1
Q

Hardy-Weinberg Conditions

A
  1. No mutations
  2. Random mating
  3. No natural selection (consistent differences)
  4. Extremely large population size (genetic drift less likely to occur)
  5. No gene flow
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2
Q

Natural Selection

A

-Differential success in survival & reproduction which leads to adaptive evolution (enhanced survival)
-Those w suitable environmental traits produce MORE OFFSPRING
(change over generations)

Can only act on existing variations: N.S. can only increase or decrease heritable traits that vary in a population

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3
Q

Genetic Drift

A

(affects the evolution)
-Chance events can cause allele frequencies to fluctuate unpredictably (especially in small populations)

Caused by the founder and bottleneck effect

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4
Q

Founder Effect

A

Small group isolated from the population to create new pop w diff gene pool

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5
Q

Bottleneck Effect

A
  1. Severe drop in the pop
  2. Certain alleles become overrepresented
  3. Low levels of genetic variation for a long time
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6
Q

Gene Flow

A

(affects the population)
-Transfer of alleles into or out of a pop due to movement of fertile individuals or their gametes
-reduces genetic differences between populations

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7
Q

Population Definition

A

Group of individuals of the same species that live in the same area which breed to produce offspring
(genetic makeup of a pop is called gene pool)

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8
Q

Formation of new alleles

A

Arise by mutation (change in nucleotide sequence of DNA)
–point mutation: change in one base (ex. sickle cell disease)
Some causes:
-errors in DNA replication
-UV light
-chemicals or radiation

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9
Q

What occurs during Sexual Reproduction that causes genetic variation?

A

Unique combination of alleles…
1. crossing over
2. random fertilization
3. independent fertilization

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10
Q

Relative Fitness

A

Given environment, traits can lead to relative fitness:

This is the contribution an individual makes to the gene pool relative to other contributions (acts more directly on phenotype)

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11
Q

Directional Selection

A

Conditions favor those w one extreme of a phenotypic range

Shifts phenotypic character in one direction

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12
Q

Disruptive Selection

A

(increases genetic variation)
Conditions favor those at both extremes over those w intermediate phenotypes

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13
Q

Stabilizing Selection

A

Acts against both extremes favors intermediate phenotypes

Reduces variation

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14
Q

Balancing Selection

A

-Heterozygote advantage: maintain 2 or more alleles at a locus (genotype) ex. sickle cell disease
INCREASES GENETIC VARIATION
-Frequency dependent selection: fitness of phenotype depends on how common it is in a population

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15
Q

Adaptation Definition

A

Inherited characteristics of organisms that enhance their survival & reproduction in specific environments
(ex. Galapagos finch beaks)

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16
Q

Artificial Selection

A

Humans modify animals by selecting & breeding desired traits (quick change)

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17
Q

Evidence of Evolution

A
  1. Evolution of drug-resistant pathogens
  2. Similarities among organism (ex. chicken vs human embryo)
  3. Fossils
  4. Biogeography: study of geographic distribution of species (continental drift)
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18
Q

Sexual Selection

A

Charles Darwin: individuals w certain inherited traits are more likely to obtain mates than other individuals

Caused by sexual dimorphism

19
Q

Sexual Dimorphism

A

Difference in secondary sexual characteristics between male & female of the same species (size, color, ornamentation, behavior)

20
Q

Sexual Selection-Intracellular & Intercellular Selection

A

Intracellular: selection within the same sex
Intercellular (mate choice): one sex (usually female) are choosy in selecting their mates

21
Q

Biological Species Concept

A

Species: group of populations whose members interbreed and do not produce viable offspring w members of other such groups REPRODUCTIVELY COMPATIBLE

22
Q

Morphological Species Concept

A

Distinguishes species by body shape & structural features

23
Q

Ecological Species Concept

A

(emphasizes the role of disruptive natural selection)
The sum of how members of a species interact w nonliving & living environment

24
Q

Allopatric Speciation

A

(geographic barriers)
Gene flow is interrupted or reduced between geographically isolated
subpopulations

25
Q

Sympatric Speciation

A

Occurs in pops that live in the same geographic location w reproductive barriers

Occurs if gene flow is reduced by such factors:
-Polyploidy: cell division that results in extra sets of chromosomes
-Habitat differentiation: when a subpop exploits a habitat or resource not used by the parent pop
-Sexual selection

26
Q

Polyploidy

A

-Much more common in plants than animals
-Polyploidy can produce new biological species in sympatry
within a single generation

27
Q

Autopolyploid

A

Indiv w/ 2 chromosome sets that are derived from a single species

The new species is fertile, but reproductively isolated from the diploid parent species

28
Q

Allopolyploid

A

Hybrid offspring

29
Q

Prezygotic Barriers

A

-Habitat Isolation (different habitats occupied)
-Temporal differences (diff reproducing times)
-Behavioral Isolation: differences in mating rituals or displays
-Mechanical Isolation (reproductive structure incompatibility)
-Gametic Isolation (sperm and egg are incompatible)

30
Q

Postzygotic Barriers

A

-Reduced hybrid viability (offspring are feeble and unable to compete for mates)
-Hybrid infertility (sterile offspring)

31
Q

What role does nondisjunction play in the formation of a fertile allopolyploid hybrid?

A

It doubles the chromosome number in the hybrid.

32
Q

Why don’t all unfavorable alleles disappear immediately from a population?

A

Because heterozygous individuals can pass on a recessive allele and create offspring that are carriers as well.

33
Q

What is required for hybrids to be fertile?

A

closely related species

The ancestors of the hybrid must be close together or the 2 hybrids mating must have the same number of chromosomes.

34
Q

Evolution Definition

A

change over time

It is limited by historical constraints: adaptations are often compromises. Evolution co-opts existing structures and adapts them to new situations

35
Q

Microevolution

A

small scale evolution within a population of a species.

36
Q

All genotype frequencies add up to…

A

1

37
Q

What does it mean when a population is in Hardy-Weinberg conditions?

A

a population that is not evolving is in Hardy Weinberg equilibrium as long Mendel’s laws are at work and random mating

38
Q

What do p and q represent?

A

We use p and q to represent alleles when there are only 2 alleles

p = dominant allele frequency
q = recessive allele frequency

39
Q

What would break Hardy-Weinberg conditions?

A

evolutionary forces like natural selection, genetic drift, gene flow

40
Q

Small populations lead to more…

A

genetic drift than large populations with less fluctuations.

41
Q

Genetic drift changes allelic frequencies within populations, leading to a reduction…

A

in genetic variation through fixation and genetic divergence among populations

42
Q

What can cause a bottleneck?

A

disease, natural disaster, fire… causes a small subset of the population to survive

43
Q

What can cause the founder effect?

A

Migration

44
Q

Macroevolution Definition

A

Origin of new groups of organisms, such as mammals, or rapid expansion of existing groups

Biology 2-Exam 1 (3 decks)

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