AP Biology Review Notes

Circadian Rhythms and Mouse Activity

  • Circadian rhythms exhibit an approximately 24-hour cycle.

  • These rhythms are controlled by both genetics and environmental conditions, including light.

  • Researchers investigated the effect of light on mouse behavior using a running wheel with a motion sensor to record activity on actograms.

  • When a mouse is active on the running wheel, the activity is recorded as a dark horizontal line on an actogram. When the mouse is inactive, no dark line is recorded.

  • Adult male mice were individually housed in cages in a soundproof room at 25°C.

  • Each mouse was provided with adequate food, water, bedding material, and a running wheel.

  • The mice were exposed to daily periods of 12 hours of light (L) and 12 hours of dark (D) (L12:D12) for 14 days, and their activity was continuously monitored.

  • After 14 days in L12:D12, the mice were placed in continuous darkness (DD), and their activity on the running wheel was recorded as before.

Predator-Prey Relationship and Evolution of Mouse Activity

  • In nature, mice are potential prey for some predatory birds that hunt during the day.

Evolution by Natural Selection

  • Charles Darwin proposed that evolution by natural selection was the basis for the differences that he saw in similar organisms as he traveled and collected specimens in South America and on the Galapagos Islands.

Darwin's Theory of Evolution by Natural Selection

  • Reproductive potential: the ability to overproduce.

  • Variability: inheritable changes or mutations linked to variability.

  • Limited resources: biotic or abiotic.

  • Competition: intraspecific struggle for existence.

  • Differential Reproduction: reproductive success of variants.

  • Generations: time needed for evolution to occur.

  • Elaboration: expansion of Darwin's ideas such as the effects of environmental change or artificial selection or good, linked example

Aspects of Evolution by Natural Selection

Convergent Evolution and Similarities Among Species

  • Different species exhibit adaptations as a result of the same environment.

  • Correct descriptive example linked to biome and survival value or linked to natural selection

Natural Selection and Resistance

  • An inherited characteristic enables the organism to resist the effect of the toxin.

  • Specific example, mechanisms of resistance, or extensive elaboration or link to natural selection.

Speciation and Isolation

  • A single population divides into two reproductively isolated populations or equivalent (use of gene pools).

  • Role of barriers in speciation or discuss gene pool separation or link to natural selection.

Natural Selection and Behavior

  • Define or describe the behavior

  • Give a clear example of how this behavior enhances survival or link to natural selection.

Natural Selection and Heterozygote Advantage

  • Survival value of heterozygote over both homozygotes

  • An example of how the heterozygous enhances the survival of the organism or link to natural selection.

Guppy Spot Study

  • Adult male guppies (Poecilia reticulata) exhibit genetically determined spots, while juvenile and adult female guppies lack spots.

  • In a study of selection, male and female guppies from genetically diverse populations were collected from different mountain streams and placed together in an isolated environment containing no predators.

  • The study population was maintained for several generations in the isolated area before being separated into two groups.

  • One group was moved to an artificial pond containing a fish predator, while a second group was moved to an artificial pond containing no predators. The two groups went through several generations in their new environments.

  • At different times during the experiment, the mean number of spots per adult male guppy was determined.

  • Vertical bars in the figure represent two standard errors of the mean (SEM).

Change in Genetic Variation

  • Genetic variation is decreasing

  • SEM gets smaller

Pigeon Lice Experiment

  • Pigeon lice (Columbicola columbae) are small parasites that feed on the feathers of the rock pigeon (Columba livia).

  • The lice are host-specific, and transmission of lice between pigeons requires direct contact.

  • Pigeons remove the lice with their beaks as they clean their feathers.

  • Researchers transferred 25 lice from a random sample of lice obtained from wild‑caught rock pigeons to each individual in groups of black pigeons and white pigeons.

  • Half of the pigeons from each color group were fitted with a harmless mouthpiece that stopped the beaks from entirely closing. The mouthpiece prevented pigeons from removing lice but did not affect the pigeons’ ability to feed.

  • Each pigeon was isolated and kept in identical environmental conditions for temperature, humidity, and amount of light. The lice have a generation time of 24 days. The researchers observed the phenotypes of the lice over a period of four years.

Phenotypic Variation

  • Increased variation increases the probability that some members of the population will survive (and reproduce) in a changing environment.

Lighting Conditions

  • Since pigeons clean their feathers by sight, variable light conditions would affect the effectiveness of this behavior.

Predicted Effect on Lice Phenotypes

  • Louse phenotypes that blended with their host’s feather color would increase in frequency.

  • Louse phenotypes that contrasted with their host’s feather color would decrease in frequency.

Reasoning

  • Lice with a contrasting coloration to the host feathers were removed before they could reproduce, while lice with a similar coloration to the host feathers survived to reproduce.

Tree Population Study

  • Researchers studying a population of trees in the forest hypothesize that warming will negatively impact the evolutionary fitness of many of the trees.

  • The researchers also hypothesize that warming will shift the range of the population further north to cooler habitats.

Evolutionary Fitness

  • It is measured by counting the number of offspring/seedlings/alleles in the next generation that came from this tree.

  • It is measured by determining the ability of a tree to produce offspring.

Range Shift and Speciation

  • The separate populations will be reproductively isolated/have no gene flow between them, and genetic differences between the populations may accumulate over time due to natural selection/genetic drift/mutations.

Effects on Soil Microbes

  • Future generations of the microbes would be composed of microbes able to reproduce at higher temperatures (shifting the gene frequency toward those alleles that enable reproduction at higher temperatures).

  • The population would go extinct.

  • The population would decrease in size.

Justification

  • The alleles that allow the microbes to survive would have been passed down to their offspring, and the alleles would become more prevalent in the population because of natural selection.

  • Microbes with different heat tolerances have different degrees of reproductive success.

  • More-heat-tolerant individuals reproduce more than do less-heat-tolerant individuals.

  • The (effective) population size will be too small/will have insufficient genetic variation to allow continued survival of the population.

  • Most of the microbes cannot reproduce (therefore there will be fewer offspring).

Prairie Community and Virus Infection

Long-Term Effects on Plant Populations and Communities

  • Plant species becomes locally extinct.

  • Reduction in genetic variability due to loss of infected plants.

  • Change in allele frequencies for the affected species.

  • Loss of consumer species dependent on affected prairie grass species.

  • Members of the affected species with a genotype conferring resistance become more common, leading to no long-term effects to the population or community.

  • Grass is replaced by other species — community is stabilized, or some changes in members of the food chain.

  • Increased erosion due to lack of grass leading to degradation of abiotic environment, further limiting the ability of the environment to support the community.

River Dolphin Phylogeny

  • River dolphins are morphologically distinct from other dolphins and are primarily restricted to freshwater ecosystems in Asia and South America.

  • Molecular studies have shown that they are less closely related than previously thought.

  • Scientists analyzed the nucleotide sequences of mitochondrial genes, including the genes for cytochrome b and two ribosomal.

Evolution of South Asian River Dolphin

  • The earliest South Asian river dolphin first evolved approximately 16 million years ago.

Lineages Sharing Node A

  • Chinese river dolphin, Amazon river dolphin, La Plata river dolphin, dolphins, narwhal, and porpoises.

Sequence Data

  • Sequence analyses of the genes would show that the genes of the La Plata river dolphin have more similarities to those of the Amazon river dolphin than to those of the Chinese river dolphin.

Morphological Similarities

  • The similarities are likely due to convergent evolution because river dolphins inhabit similar habitats and are subject to the pressures of those environments.

  • Reduced visibility in most large rivers due to silt would lead to a reduction in vision or eye size; long noses are an adaptation for searching for food; streamlined bodies and the dorsal fin are not as critical for stability in rivers as they are in the ocean.

Fossils

  • Fossils of lobe-finned fishes, which are ancestors of amphibians, are found in rocks that are at least 380 million years old.

  • Fossils of the oldest amphibian-like vertebrate animals with true legs and lungs are found in rocks that are approximately 363 million years old.

Rocks Contains Fossils

  • Rocks from 370 MYA sample.

  • Transitional fossils are found between 380 MYA (when lobe-finned fishes lived) and 363 MYA (when amphibians appeared) OR between different strata/layers in the correct order.

Evidence

  • Bones OR specific skeletal structures

    • legs /limbs/digits

    • vertebrae

    • flat skulls

    • (interlocking) ribs

    • flexible neck

  • Scales

  • Teeth

  • Other homologous structures

  • Has traits of both the lobe-finned fish and the amphibian

  • Finding the transitional fossils in the same area/same environment as either the lobe-finned fish or the amphibian

  • Molecular (DNA) evidence

Bee and Flower Relationship

  • Bees use their tongues to access nectar as a food source from the base of flowers.

  • Flowers vary in depth from shallow to deep, and bees vary in tongue length from short to long.

  • Many species of plants depend on bees to transfer pollen from one flower to another for fertilization.

Environmental Conditions

  • Low density of flowers AND low proportion of deep flowers/high proportion of shallow flowers

  • Range or point within the area of the graph less than or equal to 4 (flower density) AND less than or equal to 0.4 (proportion)

Long-tongued bees

  • Minimum value greater than or equal to 0.60

Effect on Plants with Depp Flowers

  • The proportion of plants with deep flowers will decrease.

  • The bees will not transfer pollen from the deep flowers.

  • Seed production from deep flowers decreases.

  • Plants with deep flowers will not be fertilized/pollinated/able to reproduce.

  • Bees can obtain nectar without touching the pollen.

  • Short flowers will be selected for/deep flowers will be selected against.

Genetic change

  • Phylogeny is the evolutionary history of a species.

  • The evolution of a species is dependent on changes in the genome of the species.