Zoology 101 Unit 4

Darwin's Revolution (1859)

Introduced the idea that species change over time through natural selection.

Descent with Modification

Species evolve from common ancestors, accumulating adaptations over generations.

Aristotle's view on species

Species are fixed and arranged by complexity.

Carl Linnaeus

Developed binomial nomenclature and classification systems.

Binomial Nomenclature

Classification system in which each species is assigned a two-part scientific name

Classification systems

Specific sets of objective criteria, such as offense history, previous experience in the justice system, and substance abuse patterns, applied to all inmates to determine an appropriate classification.

Georges Cuvier

Proposed catastrophism based on fossil changes over time.

James Hutton & Charles Lyell

Proposed uniformitarianism, implying the Earth is shaped by gradual processes.

Jean-Baptiste Lamarck

Proposed use/disuse and inheritance of acquired traits.

HMS Beagle Voyage

Darwin's voyage where he noted similarities between island and mainland species.

Galápagos Finches

Showed variation in beak shape linked to diet and environment.

Natural Selection

Process where individuals with advantageous traits survive and reproduce more.

Natural Selection: Key Observations

Traits vary within populations, and more offspring are produced than survive.

Natural Selection: Key Inferences

Favorable traits increase survival and accumulate over generations.

Soapberry bugs (evolution example)

Beak length adapted rapidly to changes in fruit size.

MRSA (evolution example)

Demonstrates rapid evolution of antibiotic resistance in bacteria.

Anatomical Homology

Similar structures from common ancestry, like mammalian forelimbs.

Molecular Homology

Shared genes and genetic code across different species.

Vestigial structures

Remnants of ancestral traits that serve little or no function.

Fossil Record

Shows evolutionary transitions, such as land-to-sea in cetaceans.

Biogeography

Study of species distribution influenced by continental drift.

Adaptation

An inherited trait that increases an organism's fitness.

Artificial Selection

Human-driven breeding for desired traits.

Convergent Evolution

Independent evolution of similar traits in unrelated groups.

Evolutionary Tree

Diagram showing evolutionary relationships and common ancestry.

Unit of Evolution

Populations evolve over time; individuals do not.

Origin of traits in selection

Natural selection acts on existing variation; it cannot create new traits.

Role of environment in selection

The environment determines which traits are favorable.

Microevolution

Change in allele frequencies in a population over generations.

Three mechanisms of microevolution

Natural selection, genetic drift, and gene flow.

Natural Selection

Differential survival and reproduction

Genetic Drift

Random changes in allele frequencies

Gene Flow

Movement of alleles between populations

Sources of genetic variation

Mutations, gene duplication, and sexual reproduction.

Three sources of allele recombination in sexual reproduction

Crossing over, independent assortment, and fertilization.

Phenotypic vs. Genotypic variation

Phenotypic variation affects observable traits; genotypic variation measures molecular differences.

Five conditions for Hardy-Weinberg equilibrium

No mutations, random mating, no natural selection, extremely large population, no gene flow.

Hardy-Weinberg equilibrium outcome

If all conditions are met, the population is not evolving.

Genetic Drift

Random changes in allele frequencies, having stronger effects in small populations.

Founder Effect vs. Bottleneck Effect

Founder: few individuals start a population. Bottleneck: sudden reduction in population size.

Gene Flow

Movement of alleles between populations, tending to reduce genetic differences between them.

Target of Natural Selection

Natural selection acts on phenotypes, not genotypes.

Relative fitness

The contribution an individual makes to the next generation's gene pool.

Three modes of natural selection

Directional (one extreme), disruptive (both extremes), and stabilizing (intermediate traits).

Intrasexual vs. Intersexual selection

Intrasexual: competition within one sex. Intersexual: mate choice.

Good Genes Hypothesis

The hypothesis that females prefer traits signaling genetic quality.

Balancing Selection

Selection that maintains multiple alleles in a population.

Types of balancing selection

Frequency-dependent selection (fitness depends on how common a trait is) and heterozygote advantage (heterozygotes have higher fitness).

Speciation

The process by which one species splits into two or more species.

Speciation Bridge

Bridges microevolution (allele frequency changes) and macroevolution (broad evolutionary patterns).

Biological Species Concept

Species are groups of populations that interbreed, produce viable, fertile offspring, and are reproductively isolated.

Reproductive Isolation

Biological barriers that prevent gene flow between species.

Habitat Isolation

Prezygotic barrier where species occupy different environments and rarely encounter each other.

Temporal Isolation

Prezygotic barrier where species breed at different times of day, seasons, or years.

Behavioral Isolation

Prezygotic barrier where unique courtship rituals or mating behaviors prevent interbreeding.

Mechanical Isolation

Prezygotic barrier where morphological differences prevent successful mating.

Gametic Isolation

Prezygotic barrier where sperm of one species cannot fertilize eggs of another.

Reduced Hybrid Viability

Postzygotic barrier where genes of parents impair the hybrid's development or survival.

Reduced Hybrid Fertility

Postzygotic barrier where hybrids develop but are sterile (cannot produce offspring).

Hybrid Breakdown

Postzygotic barrier where first-generation hybrids are fertile, but their offspring are feeble or sterile.

Allopatric Speciation

Speciation that occurs when geographic separation restricts gene flow between populations.

Sympatric Speciation

Speciation that occurs in populations that live in the same geographic area.

Drivers of Sympatric Speciation

Polyploidy, sexual selection, and habitat differentiation.

Hybrid Zones

Regions where members of different species meet and mate, producing mixed offspring.

Hybrid Zone: Reinforcement

Strengthening of reproductive barriers, leading to a decrease in hybrid formation.

Hybrid Zone: Fusion

Weakening of reproductive barriers, causing the two species to merge into one.

Hybrid Zone: Stability

Continued production of hybrid individuals without fusion or reinforcement.

Punctuated Equilibria

Periods of apparent evolutionary stasis punctuated by sudden change.

Gradualism

Slow, steady evolutionary change over long periods of time.

Genetics of Speciation

Can involve a single gene or multiple genes to achieve reproductive isolation.

Early Earth Conditions

Hostile environment with volcanic activity, toxic atmosphere, and no oxygen, where simple organic molecules formed.

Hydrothermal Vents Hypothesis

Theory that life began near ocean-floor vents providing heat, minerals, and chemical-rich environments.

Role of RNA in early life

Simple molecules formed RNA, which could store information, catalyze reactions, and self-replicate.

Protocells

Primitive cell-like structures formed by molecules enclosed in membranes that could grow and divide.

Evolution of early molecular systems

Natural selection favored more efficient and stable molecular systems, leading to diverse life.

Macroevolution

Evolutionary changes above the species level.

Strata

Sedimentary rock layers where most fossils are found.

Radiometric dating

Method using isotope decay to determine fossil age.

Bias in the fossil record

Favors widespread, long-lived species with hard parts.

Four eons of Earth's history

Hadean, Archaean, Proterozoic, and Phanerozoic.

Eras of the Phanerozoic eon

Paleozoic, Mesozoic, and Cenozoic.

Stromatolites

Fossilized structures representing the first life 3.5 billion years ago.

Oxygen revolution

Atmospheric oxygen accumulation occurring 2.7 to 2.4 billion years ago.

First eukaryotes

Appeared in the fossil record 1.8 billion years ago.

First multicellular eukaryotes

Appeared in the fossil record approximately 1.2 billion years ago.

Cambrian explosion

Rapid diversification of animal phyla about 535 million years ago.

Endosymbiosis theory

Mitochondria and plastids originated from engulfed prokaryotes.

Evidence for endosymbiosis

Similarities in DNA, ribosomes, and reproduction between organelles and bacteria.

Synapsids

Group of organisms from which mammals evolved.

Mammalian skeletal evolution

Gradual changes in jaw and ear bones.

First land colonizers

Prokaryotes, which arrived on land around 3.2 billion years ago.

Key animal land colonizers

Arthropods and tetrapods.

Pangaea

Supercontinent that formed 250 million years ago.

Effects of continental drift

Alters climate, habitats, and drives speciation.

Permian extinction

Mass extinction 252 million years ago caused by volcanic activity.

Cretaceous extinction

Mass extinction 66 million years ago caused by meteorite impact.

Adaptive radiation

Rapid evolution of species to fill vacant ecological niches.

Heterochrony

Evolutionary change in the timing or rate of development.

Homeotic genes (Hox genes)

Genes that control the spatial layout of body plans.

Long-term evolutionary trends

Shaped by environmental change, extinction, and evolutionary innovation.