General Biology II: Evolution, Diversity, Animal & Plant Function, and Ecology

Unit 1: Evolutionary Biology

Mechanisms of Evolution

Evolution describes the change in genetic composition of populations over time. Several mechanisms drive evolutionary change:

• Natural Selection: Differential survival and reproduction of individuals due to differences in phenotype. Favors traits that increase fitness.

• Genetic Drift: Random changes in allele frequencies, especially significant in small populations.

• Gene Flow: Movement of alleles between populations via migration, which can introduce new genetic variation.

• Mutation: Random changes in DNA sequence, the ultimate source of genetic variation.

Hardy-Weinberg Equilibrium

The Hardy-Weinberg principle provides a mathematical model to study genetic variation in populations under ideal conditions (no evolution).

• Equation: $p^2 + 2pq + q^2 = 1$ and $p + q = 1$

• Conditions: No mutation, random mating, no gene flow, infinite population size, and no selection.

Speciation and Phylogeny

• Allopatric Speciation: Occurs when populations are geographically separated.

• Sympatric Speciation: Occurs without geographic separation, often via polyploidy or behavioral changes.

• Reproductive Barriers:

  • Pre-zygotic: Prevent mating or fertilization (e.g., temporal, behavioral, mechanical isolation).

  • Post-zygotic: Prevent hybrid offspring from developing into viable, fertile adults.

• Phylogenetic Trees and Cladistics: Visual representations of evolutionary relationships; cladistics classifies organisms based on shared derived characteristics.

Evidence for Evolution

• Fossil Record: Shows changes in organisms over time.

• Comparative Anatomy & Embryology: Reveals homologous structures and developmental similarities.

• Molecular Biology: DNA and protein similarities indicate common ancestry.

• Biogeography: Geographic distribution of species supports evolutionary theory.

• Direct Observation: Evolution observed in real time (e.g., antibiotic resistance).

Unit 2: The Diversity of Life

Prokaryotes

• Domains: Bacteria and Archaea.

• Structure: No nucleus or membrane-bound organelles; circular DNA (plasmids).

• Reproduction: Binary fission (asexual).

• DNA Transfer:

  • Transduction: Gene transfer via viruses.

  • Transformation: Uptake of free DNA from environment.

  • Conjugation: Direct transfer between cells via pilus.

• Cell Wall: Bacteria have peptidoglycan; Archaea lack peptidoglycan.

• Ecological Roles: Nitrogen fixation, decomposition, symbiosis.

• Endosymbiosis: Theory that mitochondria and chloroplasts originated from prokaryotes engulfed by ancestral eukaryotes.

Protists

• Major Groups: Plant-like (algae, photosynthetic) and animal-like (protozoans, motile).

• Nutrition: Autotrophic, heterotrophic, or mixotrophic.

• Reproduction: Both sexual and asexual modes.

Fungi

• Structure: Hyphae (filaments), mycelium (network of hyphae).

• Reproduction: Sexual and asexual spores.

• Ecological Roles: Decomposers, mutualists (e.g., mycorrhizae with plants).

• Disease Impacts: Some fungi, prokaryotes, and protists cause diseases in plants and animals.

Plant Diversity and Function

• Evolution of Land Plants:

  • Nonvascular (Bryophytes/Mosses)

  • Seedless Vascular (Pterophytes/Ferns)

  • Gymnosperms

  • Angiosperms

• Alternation of Generations: Life cycle alternates between multicellular haploid (gametophyte) and diploid (sporophyte) stages.

• Basic Anatomy: Roots, stems, leaves, vascular tissues (xylem for water, phloem for sugars).

• Transport Processes:

  • Xylem: Transports water and minerals upward.

  • Phloem: Transports sugars throughout the plant.

  • Transpiration: Loss of water vapor from leaves drives water movement.

• Reproduction in Angiosperms: Flowers, pollination, seeds, and fruit formation.

Animal Diversity

• Major Phyla: Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Arthropoda, Echinodermata, Chordata.

• Key Traits: Symmetry (radial, bilateral), germ layers (diploblastic, triploblastic), coelom (body cavity), segmentation, development patterns (protostome vs. deuterostome).

Tissues and Body Plans

• Epithelial Tissue: Covers body surfaces, lines cavities; protection, absorption, secretion.

• Connective Tissue: Supports, binds, and protects organs (e.g., bone, blood, cartilage).

• Muscle Tissue: Movement; types include skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Transmits electrical signals; found in brain, spinal cord, nerves.

Homeostasis

• Negative Feedback Mechanisms: Maintain internal stability (e.g., thermoregulation, blood glucose, blood pressure, pH).

Unit 3: Animal Form and Function

Circulatory and Respiratory Systems

• Circulatory Systems: Open (hemolymph bathes organs directly) vs. closed (blood confined to vessels).

• Gas Exchange Surfaces: Gills (aquatic), lungs (terrestrial).

• Pathways: Air (respiratory tract), food (digestive tract), blood (circulatory system).

Immune System

• Innate Immunity: Non-specific, immediate defense (e.g., skin, phagocytes).

• Adaptive Immunity: Specific, slower response; involves lymphocytes (B and T cells) and antibodies.

Nervous and Sensory Systems

• Neuron Structure: Dendrites, cell body, axon.

• Action Potential: Electrical signal along axon; involves ion movement across membranes.

• Neurotransmitters: Chemical messengers between neurons.

• Hormones and Endocrine Glands: Chemical signals regulating physiology and behavior.

Motor Mechanisms & Behavior

• Innate vs. Learned Behaviors: Innate (genetically programmed), learned (acquired through experience).

• Fixed Action Patterns: Unchangeable behavioral sequences triggered by specific stimuli.

• Imprinting, Foraging, Mating Systems, Social Behavior: Various behavioral adaptations for survival and reproduction.

• Communication: Transmission of signals between individuals.

• Sliding Filament Model: Explains muscle contraction; requires ATP, involves sarcomere (contractile unit) and motor unit (neuron + muscle fibers).

Unit 4: Ecology

Population Ecology

• Density: Number of individuals per unit area.

• Dispersion: Pattern of spacing (clumped, uniform, random).

• Demographics: Statistical study of populations (age structure, sex ratio).

• Growth Models:

  • Exponential: $\frac{dN}{dt} = rN$

  • Logistic: $\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$

• Carrying Capacity (K): Maximum population size environment can sustain.

• Survivorship Curves: Type I (low death early), II (constant death rate), III (high death early).

• K- and r-selected Species: K-selected (stable, competitive), r-selected (rapid reproduction, unstable environments).

• Density Dependent/Independent Factors: Affect population growth; dependent (e.g., competition), independent (e.g., weather).

• Abiotic/Biotic Factors: Non-living vs. living influences on populations.

Community Ecology

• Interactions: Competition, predation, mutualism, parasitism.

• Trophic Structure: Feeding relationships; producers, consumers, decomposers.

• Ecological Succession: Sequence of community changes after disturbance.

• Keystone Species: Species with disproportionate effect on community structure.

Ecosystem Ecology & Energy

• Energy Flow: Movement of energy through trophic levels; primary production, food webs.

• Biogeochemical Cycles: Cycling of elements (water, carbon, nitrogen, phosphorus) through ecosystems.

Definitions

• Community: All populations of different species in an area.

• Biosphere: All regions of Earth where life exists.

• Ecosystem: Community plus abiotic environment.

Table: Comparison of Prokaryotes and Eukaryotes

Feature	Prokaryotes	Eukaryotes
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
DNA Structure	Circular (plasmid)	Linear chromosomes
Cell Division	Binary fission	Mitosis/meiosis
Cell Wall	Bacteria: peptidoglycan; Archaea: no peptidoglycan	Plants/fungi: cellulose/chitin; Animals: none

Additional info:

• Photosynthesis increased atmospheric oxygen, enabling aerobic metabolism and complex life forms.

• Horizontal gene transfer is common in prokaryotes, contributing to genetic diversity.