Boag Connect #1 (February 23 - March 8)

Front 1

Evolution

Back 1

Accumulation of inherited changes in populations over time, leading to related species

• The pattern of evolution is an accepted fact

Front 2

Darwinian Fitness

Back 2

An individual's ability to survive and reproduce relative to other members of a population

Front 3

Population

Back 3

Group of individuals of one species living in one geographic area and sharing the same gene pool

Front 4

Species

Back 4

Group of populations composed of organisms with common ancestry, sharing similar structures, functions, behaviours, etc. and able to freely interbreed in nature

Front 5

Community

Back 5

Group of species that live together and interact in a given area

Front 6

Ecosystem

Back 6

An interactive system composed of one or more communities and their abiotic (physical) environment

Front 7

Biosphere

Back 7

All of earth's ecosystems taken together

Front 8

Theory of Evolution by Natural Selection

Back 8

• Proposed by Darwin and Wallace
• Based on four observations:

1. Variation in phenotype exists among individuals

2. High reproductive potential means populations increase geometrically

3. Individuals compete for limited resources

4. 'Fit' offspring with phenotypes matching current environment more likely to reproduce

Front 9

Evidence Supporting Evolution

Back 9

• Fossil record
• Biogeography
• Selective breeding
• Convergent evolution
• Homologies (anatomical, developmental, molecular)

Front 10

Evidence for Evolution from Fossils and Geology

Back 10

• Direct evidence of evolution comes from fossils, especially in layered sediments
• Evidence shows progression of organisms through time

Front 11

Artificial Selection

Back 11

Start with starting population with some variation in phenotype, take extreme phenotype and use seed for next year

Front 12

Homologous Features

Back 12

Derive same structure in common ancestor

(look different in adult, similar in embryo)

Front 13

Homoplastic Features

Back 13

Similar functions in distantly or unrelated organisms result in convergent evolution

(look similar but no common origin)

• aka analogous traits

Front 14

Vestigial Structures

Back 14

Remnants of structures indicate adaptations wax and wane as environments change

Front 15

Convergent Evolution

Back 15

Unrelated but display structural and/or functional similarities

Front 16

Phylogeny

Back 16

Evolutionary history of a group of related species displayed as phylogenetic trees

• diagrams showing lines of descent based on molecular data

Front 17

Developmental Homology

Back 17

Species that differ as adults often bear similarities as embryos

Front 18

Adaptations

Back 18

Evolved characteristics enhancing an organism's survival or reproduction in a particular environment

Front 19

Proximate Explanation

Back 19

An immediate, mechanistic explanation not requiring evolutionary thinking

Front 20

Ultimate Explanation

Back 20

A more fundamental, historical explanation involving an evolutionary perspective

Front 21

Locus

Back 21

Plysical location on chromosome (we have to loci for each gene because we have 2 chromosomes)

Front 22

Gene Pool

Back 22

Includes all the alleles for all the loci present in the population

• Each diploid individual has a maximum oft different alleles at each locus
• summed across thousands of loci, one individual has only a small fraction of the alleles present in an entire population

Front 23

Genotype

Back 23

The combination of alleles at a given locus, on homologous chromosomes

Front 24

What is genetic variation in populations caused by?

Back 24

1. Sexual reproduction: (crossing over during meiosis)
2. Mutation: changes in DNA sequences = new alleles (cannot enter pop unless in gametes, rare)

Front 25

Balanced Polymorphism

Back 25

Situation in which two different versions of a gene are maintained in a population of organisms because individuals carrying both versions are better able to survive (heterozygote advantage)

Front 26

Frequency Dependant Selection

Back 26

Fitness of a phenotype depends on its frequency relative to other phenotypes in a given population

Front 27

Phenotypic Plasticity

Back 27

One genotype can produce different phenotypes in different environments

Front 28

Ecotype

Back 28

Partly differentiated but not enough to be a new species

Front 29

Norm of Reaction

Back 29

Continuous range of phenotypic possibilities (plasticity) for a genotype under different environmental conditions

• E.g. human height

Front 30

Morphological Traits

Back 30

Show quantitative genetic variation = multiple loci + environmental effects

Front 31

Causes of microevolution (changes in allele frequency)

Back 31

1. Mutation (origin, but weak for evolution)
2. Nonrandom mating
3. Genetic drift
4. Gene flow
5. Natural selection

Front 32

Hardy-Weinberg Principle

Back 32

Provides a 'Null Hypothesis' for what happens to gene frequencies between generations in the absence of evolution

• Explains stability of allele frequencies over successive generations in populations at genetic equilibrium with random mating

Front 33

Hardy-Weinberg Equations

Back 33

1. p+q=1 (p=frequency of dominant allele, q=frequency of recessive allele)

2. p²+2pq+q²=1

(freq. of homozygous dominant genotype + freq. of heterozygous genotype + freq. of homozygous recessive genotype = 1)

Front 34

Nonrandom Mating

Back 34

1. Inbreeding (selfing or matings b/t close relatives, can produce inbreeding depression)

2. Assortative mating common in animals (tall prefers tall)

Both eventually decrease frequency of heterozygous genotypes

Front 35

Genetic Drift

Back 35

Random changes of allele frequencies in small populations, often due to 'sampling'

• Decreases genetic variation within a population (may increase differences between populations)
• changes usually not adaptive
• Likely during bottleneck or founder effect

Front 36

Bottleneck

Back 36

A sudden decrease in population size due to environmental factors such as drought

Front 37

Founder Effect

Back 37

Genetic drift occurring when a small population colonizes a new area

Front 38

Gene Flow

Back 38

Movement of alleles by migration of individuals or gametes between populations

• Causes changes in allele frequencies, may counteract selection and inhibit local adaptation
• Or may counteract losses to genetic drift, maintaining variation

Front 39

Natural Selection

Back 39

Causes changes in phenotype frequencies, increasing those best adapted now

• Operates on phenotypes in populations
• Changes genetic composition of pop so fitness in current environment is maximized

Front 40

What are the three modes of selection on continuous (polygenic) traits?

Back 40

1. Stabilizing
2. Disruptive
3. Directional

Front 41

Stabilizing Selection

Back 41

Favours the mean or 'typical' individual

Front 42

Disruptive Selection

Back 42

Favours two or more phenotypic extremes at expense of individual near the mean

Front 43

Directional Selection

Back 43

Favours one phenotypic extreme

Front 44

Sexual Selection

Back 44

When there is competition for mates among makes (intrasexual) or when females are choosey about mates (intersexual), sexual selection may favour traits which increase male mating success