Evolution (Grade 11 AP Bio)

Sexual Selection

Theory predicting mate competition and female choice.

Sexual Dimorphism

Differences between male and female species.

Male-Male Competition

Males compete for access to mates.

Sperm Competition

Competition among sperm to fertilize eggs.

Infanticide

Males kill cubs to increase reproductive success.

Female Choice

Females select mates based on desirable traits.

Intrasexual Selection

Males compete directly for female attention.

Intersexual Selection

Females choose mates based on displays.

Combat

Physical competition between males for mates.

Male Marine Iguanas

Larger males win territory and mates.

Sperm Release

Males release more sperm for better fertilization odds.

Copulatory Plug

Substance deposited to block other males' sperm.

Damselflies

Males remove previous sperm during copulation.

Predation Risk

Showy traits increase visibility to predators.

Courtship Displays

Males perform to attract female mates.

Reproductive Success

Passing genes to future generations.

Territory Ownership

Males with larger territories attract more females.

Female Attractiveness

Males apply pheromones to influence female choice.

Cubs Weaning

Females delay breeding until cubs are independent.

Pride Dynamics

Males fight for dominance in lion prides.

Spontaneous Abortion

Females abort pregnancies when new males arrive.

Lady's Choice

Females prefer mates enhancing offspring survival.

Population Genetics

Integrates evolution with Mendelian genetics.

Allele Frequency

Proportion of specific alleles in a population.

Gene Pool

Genetic information of an entire population.

Genotype

Set of alleles in an organism.

Phenotype

Observable traits resulting from genotype.

Homozygous

Two identical alleles for a trait.

Heterozygous

Two different alleles for a trait.

Genome

Complete set of alleles in an organism.

Loci

Specific location of a gene on DNA.

Genetic Variation

Diversity of alleles within a species.

Natural Selection

Process favoring advantageous phenotypes.

Sexual Reproduction

Mixes alleles, increasing genetic diversity.

Hardy-Weinberg Principle

Model predicting allele frequencies in populations.

Dominant Allele

Allele that masks the effect of another.

Recessive Allele

Allele whose effects are masked by dominant.

Mendelian Genetics

Study of inheritance patterns of traits.

Evolution

Change in allele frequencies across generations.

Darwin's Theory

Evolution by natural selection mechanism.

Trait

Characteristic determined by genes.

Alleles

Different forms of a gene.

Recombination

Mixing of alleles during sexual reproduction.

Hardy-Weinberg Principle

Allele frequencies remain constant under specific conditions.

Allele Frequency

Proportion of a specific allele in a population.

Genotype Frequency

Proportion of a specific genotype in a population.

Dominant Allele

Allele expressed in phenotype when present.

Recessive Allele

Allele expressed only when homozygous.

p

Frequency of dominant allele A.

q

Frequency of recessive allele a.

p + q = 1

Total frequency of alleles must equal one.

p²

Frequency of homozygous dominant genotype (AA).

2pq

Frequency of heterozygous genotype (Aa).

q²

Frequency of homozygous recessive genotype (aa).

Population Size

Total number of individuals in a population.

Mating Opportunities

Equal chances for all individuals to mate.

No Mutations

Genetic changes must not occur.

No Migration

No individuals entering or leaving the population.

No Natural Selection

All individuals have equal reproductive success.

Genotype

Genetic constitution of an individual.

Phenotype

Observable traits of an individual.

Hardy-Weinberg Equation

Mathematical formula for predicting genotype frequencies.

Next Generation Frequencies

Proportions of genotypes in subsequent generations.

Evolutionary Implications

Changes in allele frequencies indicate evolutionary processes.

Sample Question

Example problem to apply Hardy-Weinberg calculations.

Eye Colour Alleles

Red (W) dominant, white (w) recessive in fruit flies.

Adaptation

A trait that increases the reproductive fitness of its possessor; i.e. More of their genes are passed on since they are more likely to survive to reproductive age.

Criteria for Adaptation

Before we can classify something as an adaptation we need to determine what a trait is for and show that individuals possessing that trait contribute more genes to future generations than organisms lacking it.

Giraffe's Long Neck

An example of adaptation where the giraffe's long neck allows it to reach higher trees, but also presents disadvantages such as difficulty bending down to get water.

Giraffe Foraging Behavior

Giraffes spend much of their dry-season foraging time browsing on low bushes, not tall trees, and prefer to feed at shoulder height.

Hypothesis for Long Neck Evolution

A possible hypothesis is that long necks evolved as a weapon, as male giraffes sometimes fight using their heads as clubs.

Male Giraffe Neck Comparison

Male giraffes have necks that are 30-40 cm longer and 1.7 times heavier than females.

Head Weight Comparison

Males have heads that are armored and 3.5 times heavier than females.

Reproductive Success of Long Neck Giraffes

Longer neck giraffes had more reproductive success not because they ate more, but because they intimidated smaller males and attracted more mates.

Female Giraffe Neck Length

Females have long necks because males pass on their genes to their daughters too.

Adaptation Definition

A structure, behaviour or physiological process that helps an organism survive and reproduce in a particular environment.

Stick Insect Adaptation

The stick insect is able to survive because it blends in with the tree (camouflage).

Owl Adaptation

This owl has a specific adaptation of fluffy wings that do not make a lot of noise.

Survival of the Fittest

Challenges that limit survival include severe weather, famine, competition (food, space, and mates), and disease.

Extinction

Extinct: when a species disappears completely from Earth.

Types of Adaptation

3 Main Types of Adaptation: Structural Adaptation, Behavioural Adaptation, and Physiological Adaptation.

Structural Adaptation

Physical features of an organism, e.g., beak on a bird, ability to camouflage, mimicry.

Mimicry

Harmless species physically resemble a harmful species; predators avoid the harmless species as much as they do the harmful one.

Behavioural Adaptation

Things organisms do to survive. E.g. bird calls or migration.

Physiological Adaptation

Changes or chemical reactions that occur within an organism. E.g. Hibernation allows organisms to survive by slowing down metabolism and preserving their energy.

Development of Adaptations

Gradual, accumulative changes that help an organism survive and reproduce, resulting from random, heritable mutations in DNA that accumulate over generations.

Variations

Differences (structural, functional, or physiological) between individuals.

Environmental Conditions

Determine if variation is (+), (-), or neutral.

(+)

Survival; pass on to offspring and increase the trait in the population.

Case Study: The English Peppered Moth

3 colour variations of moths: White flecked with black dots, Black, Intermediate colour.

Mid 1800's Black Moths

Were rare in Manchester; 50 years later, 95% of moths were black in Manchester, but less frequent in rural areas.

The English Peppered Moth Explanation

The proportion of flecked and black moths changed in response to changes in the environment.

Camouflage in Moths

In the mid 1800's light coloured moths were camouflaged in the trees; 50 years later, pollution/soot caused darker trees, allowing dark moths to survive.

Variation Within Species

Created by the different combination of alleles that are inherited from parents.

Mutation

A random permanent change in the genetic material of an organism and is the only source of new genetic variation.

Kittens' Fur Variation

The kittens in this litter have different fur colour and patterns, partly because each kitten inherited a different combination of alleles from its parents.

Variations Within Humans

Humans have lots of variation due to random combinations of alleles from parents.

Different Combinations of Alleles

Contribute to different phenotypes.

Selective Advantage

A genetic advantage that improves an organism's chance of survival, usually in a changing environment. Example: Antibiotic Resistance.

Antibiotic Resistance

Organisms that reproduce rapidly can see a change in allele frequencies quickly; a gene that may have been rare can become common in a short period of time if it provides a significant advantage.