General Biology II Exam Summary

Overview

Summary of General Biology 2 topics: domains of life, cell types, major kingdoms, physiology, behavior, and ecosystems.
Emphasis on key definitions, structures, processes, and examples for exam study.

Domains Of Life And Cell Types

Three domains: Bacteria, Archaea, Eukaryotes.
Prokaryotes: Bacteria + Archaea; unicellular, binary fission, no nucleus.
Eukaryotes: multicellular or unicellular, mitosis/meiosis, nucleus and membrane-bound organelles.
Archaea genetically closer to eukaryotes.

Bacteria: Classification And Cell Wall

Classified by metabolism, shape, growth environment, gene sequence, cell wall structure.
Peptidoglycan is unique to bacteria.
Gram-positive: single membrane, thick peptidoglycan, stains purple (e.g., Staphylococcus aureus).
Gram-negative: two membranes with peptidoglycan between, stains pink (e.g., E. coli, cyanobacteria).
Antibiotics can inhibit peptidoglycan synthesis.
Lateral (horizontal) gene transfer exchanges genes between prokaryotes.
Use stable core genes to infer phylogeny.
Bacterial communities: biofilms — cells secrete sticky polysaccharide matrix (dental plaque, implants, lenses).

Archaea: Membrane Features

Distinct lipid structure: ether linkages (not ester).
Membranes often form monolayers rather than bilayers.

Viruses

Not definitively classified as living; require host to replicate.
Structure: DNA or RNA core, protein envelope with surface proteins to bind host cells.
Replicate using host machinery.

Endosymbiotic Theory And Eukaryotic Organelles

Eukaryotic organelles (mitochondria, plastids) derived from ancestral engulfed bacteria.
Primary endosymbiosis: direct engulfment of bacteria.
Secondary endosymbiosis: engulfment of a eukaryote that already contained endosymbionts.
Engulfment via phagocytosis → formation of vacuole/phagosome from plasma membrane.

Protists

Eukaryotes that are not plants, animals, or fungi.
Mostly unicellular; some multicellular.
Include plankton, phytoplankton, autotrophs, heterotrophs.
Diatoms: photosynthetic, silicon in cell walls, contribute to fossil fuels.
Dinoflagellates: photosynthetic, two flagella, can cause toxic red tides.

Fungi

Synapomorphies: absorptive heterotrophy and chitin in cell walls.
Forms: multicellular (mushrooms) and unicellular (yeast).
Structure: mycelium (network) made of hyphae (filaments); mushrooms are spore-producing fruiting bodies.
Ecological roles: saprotrophic (decomposers), parasitic, pathogenic, mutualistic (mycorrhizae).
Reproduction: sexual and asexual; life stages include haploid (n), dikaryotic (n+n), diploid (2n).

Animals: Characteristics And Development

Traits: multicellularity, heterotrophy, internal digestion, movement.
Origin: choanoflagellate-like ancestor; sponges as simple animals.
Body symmetry: asymmetry, radial, bilateral.
Germ layers: diploblasts (2), triploblasts (3).
Triploblasts subdivide: protostomes (mouth first) and deuterostomes (mouth later).
Deuterostome groups: echinoderms, hemichordates, chordates.
Vertebrates: backbone; amniotes (reptiles, birds, mammals) produce amniotic eggs.
Mammal features: sweat glands, mammary glands, hair, four-chambered heart.

Plants: Types, Adaptations, Life Cycle

Multicellular autotrophs with cell walls, mitochondria, plastids.
Groups: algae and green plants; green plants include land plants.
Land plant categories: non-vascular (mosses) and vascular.
Vascular plants: seedless and seed plants; seed plants subdivided into gymnosperms (non-flowering) and angiosperms (flowering).
Key land adaptations: protected embryo, waxy cuticle, stomata, symbiosis with fungi (mycorrhizae).
Alternation of generations: gametophyte (haploid, photosynthetic) and sporophyte (diploid, nutritionally dependent on gametophyte in some groups).

Flowering Plants: Photoreceptors And Flowering Control

Photoreceptors contain phytochromes absorbing red (Pr) and far-red (Pfr) light.
Phytochrome interconverts: Pr ↔ Pfr; prolonged darkness converts Pfr to Pr.
Long-day plants flower when nights are shorter than threshold (require more daylight).

Photosynthesis: Light Reactions And Carbon Fixation

Converts sunlight + CO2 → sugars + O2.
Two stages: light reactions (thylakoid membranes) and carbon fixation (stroma).
Chlorophyll absorbs light, initiates electron transport chain producing ATP and O2.
Rubisco enzyme catalyzes CO2 fixation to form carbon intermediates used to make glucose.

Animal Metabolism And Temperature Regulation

Metabolic rate: energy consumption rate; measured by oxygen consumption.
Regulators (endotherms): maintain stable internal temperature (mammals, birds).
Conformers (ectotherms): internal temperature matches environment (frogs, lizards, many fish).
Thermoregulation mechanisms: shivering, vasoconstriction, panting, sweating.
Insulation differences: cold-climate animals have more fat/fur; hot-climate animals have less insulation and larger surface area.
Homeostasis via negative feedback (maintain set point) and positive feedback (amplify process, e.g., childbirth via oxytocin).

Endocrine System: Glands And Hormones

Exocrine glands: secrete through ducts (e.g., sweat glands).
Endocrine glands: secrete hormones into blood (pituitary, thyroid, adrenal).
Hormones: slow-acting chemical messengers binding target receptors.
Pituitary gland: connected to hypothalamus, "master gland"; anterior and posterior lobes.
Posterior pituitary: releases oxytocin.
Anterior pituitary: secretes hormones regulating adrenal (ACTH), thyroid (TSH), and reproduction (FSH, LH).
Gonads produce sex hormones: progesterone, estrogen, testosterone; regulate gamete formation.
Female cycles: ovarian cycle (~28 days), menstrual cycle (uterine lining changes); embryo releases progesterone, estrogen, and hCG (pregnancy marker).

Digestive System: Regions And Functions

Functions: digest/absorb nutrients, reabsorb water and salts, eliminate waste.
Foregut: mouth, esophagus, stomach (acid and protein digestion).
Midgut: small intestine (completes protein/carbohydrate digestion, begins fat digestion, main nutrient absorption).
Hindgut: large intestine (water reabsorption), rectum, bladder for excretion.
Accessory organs: pancreas (enzymes, insulin/glucagon), liver (detoxification), gallbladder (bile storage).
Blood sugar regulation: glucagon raises blood glucose; insulin lowers blood glucose and promotes glycogen storage.

Respiratory And Circulatory Systems

Breathing: diaphragm contracts to expand chest cavity and inhale; relaxes to exhale.
Gas exchange in alveoli: O2 → blood, CO2 → lungs to be exhaled.
Circulatory system transports gases, nutrients, wastes.
Mammalian heart: four chambers separate oxygenated and deoxygenated blood.
Cardiac circuit: lungs → pulmonary veins → left atrium → left ventricle → aorta → body → vena cava → right atrium → right ventricle → pulmonary artery → lungs.
Cardiac cycle phases: diastole (relaxation, filling) and systole (contraction, ejection).
Heart sounds ("lub-dub") due to atrioventricular valve closure.
Veins carry blood to heart; arteries carry blood away.

Capillary Exchange And Pressures

Capillaries: site of exchange for glucose, O2, CO2, solutes.
Fluid compartments: blood plasma (in capillaries) and extravascular fluid (outside).
Forces governing exchange: hydrostatic pressure (blood pressure) and oncotic pressure (protein osmotic pressure).
Four opposing pressures: capillary hydrostatic, capillary oncotic, tissue hydrostatic, tissue oncotic.
Net movement depends on combined pressures.

Neurons And Membrane Potentials

Neuron parts: dendrites (receive signals), cell body (integrates), axon (conducts), axon terminal (transmits).
Resting and action potentials depend on charge difference across membrane.
Major ions: Na+ (sodium), K+ (potassium), Cl- (chloride), Ca2+ (calcium).
Movement of ions into/out of cells changes membrane charge, triggering firing.
Further study recommended in neurobiology resources.

Immune System

Purpose: distinguish self from non-self and destroy pathogens.
Innate immunity: fast, non-specific (skin, mucous, cytokines, phagocytes).
Acquired (adaptive) immunity: slower, specific; includes humoral and cell-mediated responses.
Humoral response: memory B cells → plasma B cells produce specific antibodies.
Cell-mediated response: cytotoxic T cells bind and destroy infected cells.
Both arms participate in viral defense (e.g., SARS-CoV-2).

Animal Behavior: Causes And Examples

Proximate causes: immediate physiological mechanisms for behavior (how).
Ultimate causes: evolutionary reasons for behavior (why).
Fixed action patterns: innate, stereotyped behaviors completed once initiated (e.g., spider web weaving).
Learning: behavior modification from experience (classical conditioning — Pavlov).
Imprinting: rapid attachment during critical period (e.g., ducklings).
Social communication example: bee waggle dance conveys food location.
Hormonal effects: oxytocin promotes bonding and parental care.

Ecosystems, Diversity, And Trophic Cascades

Ecosystem: organisms in habitat + physical environment.
Community diversity metrics: richness (number of species) and evenness (relative abundance).
Community composition changes due to colonization, extinction, natural events, human influence.
Trophic structure: primary producers (plants) → primary consumers (herbivores) → omnivores → secondary/tertiary consumers.
Trophic cascades: changes at one trophic level affect others due to interconnected food web dynamics.

Action Items / Next Steps

Review key terms: prokaryote, eukaryote, peptidoglycan, endosymbiosis, gametophyte, sporophyte, phytochrome, rubisco.
Memorize major organ systems and their primary functions.
Practice drawing the cardiac circuit and alternation of generations cycle.
Solve practice questions on membrane potentials and capillary exchange pressures.