Biology - Lecture Exam 3 Study Guide

What is the definition of evolution?

The process of change in inherited traits within a population over generations; “descent with modification.”

What is microevolution?

Small-scale changes in allele frequencies within a population over time.

What is macroevolution?

Large-scale evolutionary changes that produce new species or taxonomic groups.

What is a genotype?

The genetic makeup or alleles an organism carries.

What is a phenotype?

The observable physical traits resulting from genotype and environment. Natural selection acts on phenotypes.

What are the five mechanisms of evolution?

Mutation, Natural Selection, Gene Flow, Genetic Drift, Sexual Selection.

What is a mutation?

A permanent change in DNA that introduces new alleles and variation in a population.

What is natural selection?

When individuals with advantageous traits survive and reproduce more successfully, passing those traits to offspring.

Give two examples of natural selection.

Peppered moths evolving darker color; Darwin’s finches evolving different beak sizes.

What is gene flow?

Movement of alleles between populations via migration or gametes.

Does gene flow make populations more similar or different?

More similar.

How does gene flow prevent speciation?

By maintaining genetic connection between populations.

What is genetic drift?

Random change in allele frequencies due to chance, strongest in small populations.

What are two types of genetic drift?

• Bottleneck effect: Population size drops sharply, losing genetic diversity.

• Founder effect: A new population forms from a small number of individuals.

What is sexual selection?

When certain traits increase mating success through competition or mate choice.

What is directional selection?

Favors one extreme trait, shifting the population.
Example: Peppered moths becoming darker.

What is stabilizing selection?

Favors intermediate traits, reducing variation.
Example: Peacock tails—too short or too long are less fit.

What is disruptive selection?

Favors both extremes, may lead to new species.
Example: African seed cracker finches (small & large beaks).

What is biological fitness?

The ability of an organism to survive and reproduce successfully.

What is an adaptive trait?

A heritable feature that improves fitness in an environment.

What is coevolution?

Two or more species evolve in response to each other (e.g., bats and moths).

What is convergent evolution?

Unrelated species evolve similar traits; produces analogous structures.

What is divergent evolution?

Related species evolve different traits; produces homologous structures.

List the six types of evidence for evolution.

Artificial selection, Fossil record, Comparative anatomy, Genetic evidence, Biogeography, Embryonic development.

What is artificial selection?

Humans breed species for desired traits (dogs, crops).

What is the Principle of Superposition?

Older rock layers are below younger ones, showing fossil age.

What are transitional fossils?

Fossils showing intermediate stages between ancestors and descendants.

What are homologous structures?

Traits with same origin but different functions (e.g., bat wing and human arm).

What are analogous structures?

Traits with same function but different origin (e.g., insect wing and bird wing).

What are vestigial structures?

Traits that have lost original function (e.g., wisdom teeth, tailbone).

What is genetic evidence for evolution?

All life shares DNA and similar genetic codes; humans share 98.8% of DNA with chimpanzees.

What is biogeography?

Study of species distribution; explains related species on different continents.

What do similarities in embryonic development show?

Common ancestry among species.

What is the Biological Species Concept?

Species are groups that can interbreed and produce fertile offspring.

What are limitations of the Biological Species Concept?

Doesn’t apply to asexual or extinct species; hybrids blur boundaries.

What is allopatric speciation?

New species form due to geographic isolation.
Example: Salamanders separated by a valley.

What is sympatric speciation?

New species form in same area due to ecological isolation or polyploidy.
Example: Apple maggot flies.

What are prezygotic barriers?

Prevent mating or fertilization (behavioral or mechanical isolation).

What are postzygotic barriers?

Occur after fertilization—hybrids may be sterile or unfit (e.g., mules).

What is the hierarchical classification system (most to least inclusive)?

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

What are the two parts of binomial nomenclature?

Genus and species (e.g., Homo sapiens).

What is a clade?

A group including an ancestor and all its descendants.

What are sister taxa?

Two groups that share a recent common ancestor.

What are nodes on a phylogenetic tree?

Represent common ancestors.

Major Events in Life’s History

Event	Time
First life (prokaryotes)	3.5 bya
Oxygen appears	2.6 bya
First eukaryotes	1.8 bya
Multicellularity	1.3 bya
Animals evolve	600 mya
Plants/fungi on land	500 mya
Animals on land	450 mya
Humans evolve	200,000 years ago

What is the Endosymbiotic Theory?

Eukaryotes evolved when larger cells engulfed smaller bacteria that became organelles (mitochondria, chloroplasts).

What are the three domains of life?

Bacteria, Archaea, Eukarya.

When did life first appear on Earth?

3.5 billion years ago (stromatolites).

What is a biofilm?

A sticky community of microbes on a surface.

What does flagella do?

Provides movement.

What are three methods of genetic recombination in bacteria?

Transformation, Transduction, Conjugation.

What is microbial remediation?

Using bacteria to clean pollution (e.g., oil spills).

How are bacteria beneficial?

Aid digestion, make food, antibiotics, recycle nutrients.

What is a protist?

Any eukaryote not classified as plant, animal, or fungus; mostly single-celled.

How do protists move?

By flagella, cilia, or pseudopodia.

Why are plankton important?

They form the base of aquatic food webs and produce oxygen.

What are fungal cell walls made of?

Chitin.

How do fungi obtain nutrients?

Secrete enzymes, digest externally, and absorb nutrients.

What are mycorrhizae fungi?

Symbiotic fungi that exchange nutrients with plant roots.

Why are decomposers important?

Recycle nutrients, return them to the ecosystem.

What are characteristics all plants share?

Multicellular, photosynthetic, cell walls of cellulose.

What adaptations helped plants colonize land?

Roots, waxy cuticle, stomata, vascular tissue.

What does xylem do?

Transports water and minerals.

What does phloem do?

Transports sugars.

What is primary growth?

Growth in length at apical meristems.

What is secondary growth?

Growth in thickness for support.

Which plants produce seeds?

Gymnosperms & Angiosperms.

Which plants produce fruits?

Angiosperms.

Which first evolved pollen and seeds?

Gymnosperms.

Four Major Plant Groups

Group	Key Traits	Example
Bryophytes	Nonvascular, use spores, live near water	Mosses
Ferns	Vascular, seedless, reproduce by spores	Ferns
Gymnosperms	Vascular, seeds in cones, pollen	Pines
Angiosperms	Vascular, flowers & fruits	Roses, grasses

What are the nine major animal phyla?

Porifera, Cnidaria, Platyhelminthes, Mollusca, Annelida, Nematoda, Arthropoda, Echinodermata, Chordata.

What type of symmetry do sponges have?

Asymmetry.

Which phyla have radial symmetry?

Cnidaria, adult Echinoderms.

Which phyla have bilateral symmetry?

Most others (worms, arthropods, chordates).

Which phylum represents most species on Earth?

Arthropoda.

What defines chordates?

Notochord (support) and dorsal nerve cord (spinal cord).

What helped chordates adapt to land?

Lungs, amniotic egg, water-saving systems.

Mammals

Type	Placenta	Example
Monotremes	None; lay eggs	Platypus
Marsupials	Simple; pouch	Kangaroo
Eutherians	Complex; full gestation	Humans

What traits define primates?

Opposable thumbs, flexible joints, flat nails, large brains.

What is bipedalism?

Walking upright on two legs.

What is the Out of Africa hypothesis?

Modern humans evolved in Africa and migrated worldwide ~60–70k years ago.