Biology Final Exam

What are the levels of ecological organization?

Organism → Population → Community → Ecosystem → Landscape → Biosphere

What do ecologists study at each level?

Organism (behavior/physiology), Population (size/growth), Community (species interactions), Ecosystem (energy/nutrients), Biosphere (global processes)

How does Earth’s tilt affect seasons?

Tilt causes varying sunlight angles → seasonal temperature changes

How do mountains affect climate?

Rain shadow effect → wet windward side, dry leeward side

What determines biome distribution?

Climate (temperature + precipitation) and disturbance (fires, storms)

Difference between abiotic and biotic factors?

Abiotic = nonliving (temp, water); Biotic = living (predators, competition)

How will climate change affect species?

Shift ranges poleward or to higher elevations

Key terrestrial biomes?

Desert, savanna, tropical forest, temperate forest, taiga, tundra

Key aquatic biomes?

Freshwater (lakes, rivers), marine (oceans, coral reefs, estuaries)

Density vs dispersion?

Density = individuals per area; Dispersion = spacing (clumped, uniform, random)

Carrying capacity (K)?

Max population size environment can sustain

Why is human K hard to determine?

Technology & resource use constantly change it

Density-dependent factors?

Competition, disease, predation

Density-independent factors?

Weather, natural disasters

Age pyramid meanings?

Wide base = growth; narrow = decline; even = stable

Types of species interactions?

Competition (-/-), Predation (+/-), Mutualism (+/+), Commensalism (+/0), Parasitism (+/-)

Ecological niche?

Species’ role + resource use

Competitive exclusion principle?

Two species cannot occupy same niche long-term

Resource partitioning?

Species divide resources to coexist

Character displacement?

Traits diverge due to competition

Trophic cascade?

Top predator affects entire food web

Keystone species?

Disproportionately large effect on ecosystem

Dominant species?

Most abundant/high biomass

Primary vs secondary succession?

Primary = no soil; Secondary = soil remains

1st law of thermodynamics?

Energy conserved

2nd law of thermodynamics?

Energy lost as heat → inefficiency

Why only ~10% energy transfer?

Lost as heat/metabolism

Why less biomass at top trophic levels?

Energy loss limits higher levels

Role of decomposers?

Recycle nutrients back to ecosystem

Nitrogen cycle key step?

Nitrogen fixation (bacteria convert N₂ → NH₃)

Human impact on nitrogen cycle?

Fertilizers → eutrophication

Carbon cycle importance?

Regulates climate

Cause of climate change?

Increased CO₂ from fossil fuels

Value of biodiversity?

Food, medicine, ecosystem stability

Species richness vs diversity?

Richness = number of species; Diversity = richness + evenness

Four major threats (HIPPO)?

Habitat loss, Invasive species, Pollution, Overharvesting (+ climate change)

Small population risks?

Inbreeding, genetic drift

Declining population approach?

Focus on environmental causes

Species vs landscape conservation?

Species = individual focus; Landscape = habitat/ecosystem focus

Three domains?

Bacteria, Archaea, Eukarya

Three kingdoms (basic)?

Plantae, Animalia, Fungi (all Eukarya)

Hypothesis vs theory?

Hypothesis = testable idea; Theory = well-supported explanation

Independent vs dependent variable?

Independent = manipulated; Dependent = measured

What does p < 0.05 mean?

Statistically significant difference

Lamarck vs Darwin?

Lamarck = acquired traits; Darwin = natural selection

Natural selection requires?

Variation, heritability, overproduction, differential survival

Adaptation?

Trait increasing fitness

Four mechanisms of evolution?

Mutation, gene flow, genetic drift, natural selection

Only mechanism causing adaptation?

Natural selection

Relative fitness?

Reproductive success

Types of selection?

Directional (favors one extreme), stabilizing (favors average), disruptive (favors both extremes)

Biological species concept?

Can interbreed and produce viable offspring

Prezygotic vs postzygotic?

Pre = before fertilization; Post = after

Allopatric vs sympatric speciation?

Allopatric = geographic separation; Sympatric = same area

Oldest life?

~3.5 billion years (prokaryotes)

When did oxygen increase?

Cyanobacteria photosynthesis

Cambrian explosion?

Rapid diversification of animal phyla

Taxonomic order?

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

Monophyletic group?

Common ancestor + all descendants

Archaea vs Bacteria?

Archaea = extreme environments; Bacteria = common

Importance of prokaryotes?

Nutrient cycling, nitrogen fixation

Protists?

Diverse eukaryotes (not a single kingdom)

Key plant adaptations?

Cuticle, stomata, vascular tissue

Xylem vs phloem?

Xylem = water; Phloem = sugars

Transpiration?

Water movement driven by evaporation

Seeds & pollen function?

Protection & reproduction without water

How do fungi eat?

Absorption after external digestion

Role of fungi?

Decomposers

Four chordate traits?

Notochord, dorsal nerve cord, pharyngeal slits, post-anal tail

Most diverse animal group?

Invertebrates (especially arthropods)

Amniote adaptation?

Amniotic egg allows land reproduction

Evidence for evolution

• Fossils

• Homology (same structure, different function)

• Analogous traits (different structure, same function)

• Molecular (DNA similarities)

3 eons

• Archean → first life (prokaryotes)

• Proterozoic → oxygen rises, eukaryotes appear

• Phanerozoic → modern life

Mass extinctions

• Permian → largest extinction

• Cretaceous → dinosaurs wiped out

Phylogenetic trees

Branch point = common ancestor

Sister taxa = closest relatives

Monophyletic group = ancestor + all descendants

Outgroup = reference group

Groups:

• Diatoms → photosynthetic

• Dinoflagellates → red tides

• Apicomplexans → parasites

• Red/Green algae → ancestors of plants

• Amoebozoans → amoebas

• Choanoflagellates → closest to animals

Plant groups

• Nonvascular (mosses)

• Seedless vascular (ferns)

• Gymnosperms (cones)

• Angiosperms (flowers)

Reproduction

• Gametophyte = produces gametes

• Sporophyte = produces spores

Body plans

Symmetry (radial vs bilateral)

Tissue layers (Ectoderm, mesoderm, endoderm)

Body cavity (Coelom, pseudocoelom, acoelomate)

Mammal types

Monotremes → egg-laying

Marsupials → pouch (Australia dominant)

Eutherians → placental (most diverse)