Chapter 14: Speciation and Evolutionary Processes

Microevolution, Speciation, and Macroevolution

• Microevolution: Small-scale changes in allele frequencies within a population over generations, often due to mutation, natural selection, gene flow, and genetic drift.

• Speciation: The process by which one species splits into two or more distinct species, typically through reproductive isolation.

• Macroevolution: Large-scale evolutionary changes that occur over long periods, leading to the emergence of new taxonomic groups above the species level.

• Example: The diversification of Darwin's finches on the Galápagos Islands illustrates speciation and adaptive radiation.

Reproductive Isolation Mechanisms

• Pre-zygotic barriers: Prevent mating or fertilization between species (e.g., temporal, habitat, behavioral, mechanical, and gametic isolation).

• Post-zygotic barriers: Occur after fertilization, reducing hybrid viability or fertility (e.g., hybrid inviability, hybrid sterility, hybrid breakdown).

• Example: Mules (horse-donkey hybrids) are sterile, a post-zygotic barrier.

Role of Evolutionary Forces

• Natural Selection: Differential survival and reproduction of individuals due to differences in phenotype.

• Adaptation: Traits that enhance survival and reproduction in a specific environment.

• Meiosis: Generates genetic variation through recombination and independent assortment.

• Mutation: Source of new genetic variation.

Mechanisms of Speciation

• Allopatric Speciation: Occurs when populations are geographically separated, leading to divergence.

• Sympatric Speciation: Occurs without geographic separation, often via polyploidy or ecological niche differentiation.

• Punctuated Equilibrium: Evolutionary change occurs in rapid bursts, separated by periods of stasis.

• Gradualism: Evolutionary change occurs slowly and steadily.

• Polyploidy: Formation of organisms with extra sets of chromosomes (e.g., diploid, triploid, tetraploid), common in plants.

• Hybrid Zones: Regions where different species meet and mate, producing hybrids; outcomes include reinforcement, fusion, or stability.

Sexual Selection and Speciation

• Sexual Selection: Non-random mating based on traits that increase mating success, potentially leading to reproductive isolation (e.g., cichlid fish in Lake Victoria).

Data Analysis

• Ability to interpret graphs and tables related to evolutionary processes is essential.

Chapter 15: Origin of Life and Earth's History

Origin of Life

• Pasteur's Experiment: Demonstrated that life does not spontaneously arise from non-living matter; life arises from pre-existing life.

• Prebiotic Synthesis: Formation of organic molecules (monomers and polymers) under early Earth conditions, possibly near hydrothermal vents or via lightning in a reducing atmosphere.

Macromolecules in Early Evolution

• RNA World Hypothesis: Early life may have used RNA for both genetic information and catalysis.

• DNA: More stable genetic material evolved later.

• Proteins: Serve as enzymes and structural molecules.

Geologic Time Scale

• Major Eras: Precambrian, Paleozoic, Mesozoic, Cenozoic.

• Major Events: Appearance of prokaryotes, eukaryotes, multicellular life, land colonization, mass extinctions.

Taxonomic Hierarchy

• Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species

Continental Drift and Earth's Structure

• Pangea: Supercontinent that split into modern continents.

• Mantle: Layer beneath Earth's crust.

• Crust: Earth's outermost solid layer.

• Strata: Layers of sedimentary rock.

• Biosphere: All regions of Earth inhabited by life.

Radioactive Dating

• Radioactive Isotopes: Unstable atoms that decay at a constant rate.

• Carbon Dating: Used to date fossils up to about 50,000 years old.

Evolution of Multicellularity

• Large multicellular organisms evolved from small unicellular ancestors through cell specialization and cooperation.

Phylogenetic Trees

• Constructed using morphological and molecular data to depict evolutionary relationships.

Adaptive Radiation

• Rapid diversification of a lineage into multiple forms adapted to different environments.

Chapter 10: Viruses and Gene Transfer

Viruses: Structure and Life Cycle

• Viruses are not living organisms: They lack cellular structure, metabolism, and cannot reproduce independently.

• Origins and Spread: May have evolved from mobile genetic elements; spread via infection of host cells.

• Components: Genetic material (DNA or RNA), protein coat (capsid), sometimes a lipid envelope.

• Envelope: Helps viruses enter host cells.

• Capsid: Protects viral genetic material.

Viral Infection Cycles

• Lytic Cycle: Virus replicates and lyses host cell.

• Lysogenic Cycle: Viral DNA integrates into host genome (prophage), replicates with host.

• Prophage vs. Phage: Prophage is viral DNA in host genome; phage is the virus particle.

Types of Viruses

• DNA Viruses: Use host machinery to replicate DNA.

• RNA Viruses: Often replicate in cytoplasm; may use reverse transcriptase (e.g., HIV).

HIV Infection

• HIV is an RNA virus that infects immune cells, integrates into host DNA, and can remain latent.

Gene Transfer in Bacteria

• Conjugation: Direct transfer of DNA between bacteria via pilus.

• Transformation: Uptake of free DNA from environment.

• Transduction: Transfer of DNA by bacteriophages.

• R Plasmid: Plasmid carrying antibiotic resistance genes.

Chapter 16: Prokaryotes and Protists

Classification and Domains

• Prokaryotes: Belong to domains Bacteria and Archaea.

• Eukaryotes: Kingdoms include Protista, Fungi, Plantae, Animalia.

Bacterial Structure and Types

• Endospores: Dormant, resistant cells formed by some bacteria.

• Gram-positive vs. Gram-negative: Differ in cell wall structure; Gram+ have thick peptidoglycan, Gram- have thin peptidoglycan and outer membrane.

• Examples: Anthrax (Bacillus anthracis), Botulinum (Clostridium botulinum), Salmonella, Cyanobacteria (photosynthetic bacteria).

Bacterial Toxins and Biofilms

• Endotoxins: Released from outer membrane of Gram- bacteria.

• Exotoxins: Secreted proteins causing disease.

• Biofilm: Community of microorganisms attached to a surface.

Prokaryotic Metabolism and Ecology

• Bioremediation: Use of organisms to remove pollutants.

• Nitrogen Fixation: Conversion of atmospheric nitrogen to ammonia by bacteria.

• Symbiosis: Close association between different species.

• Endosymbiosis: One organism lives inside another; origin of mitochondria and chloroplasts.

Classification by Energy Source

• Photoautotrophs: Use light and CO2.

• Chemolithoautotrophs: Use inorganic chemicals and CO2.

• Chemoheterotrophs: Use organic compounds for energy and carbon.

Archaea and Eukarya

• Similarities: Both have some similar genes and metabolic pathways.

• Types of Archaebacteria: Methanogens (anaerobic, produce methane), Halophiles (salty environments), Thermophiles (hot environments).

Protists

• Heterotrophic Protists: Obtain food by ingestion or absorption.

• Photoautotrophic Protists: Perform photosynthesis (e.g., algae).

• Life Cycle of Algae: Alternation of generations between haploid and diploid stages.

• Symbiosis with Corals: Zooxanthellae (dinoflagellates) live in coral tissues.

Eukaryote Phylogeny

• SAR: Stramenopiles, Alveolates, Rhizarians.

• Excavata: Includes euglenids, diplomonads.

• Unikonta: Includes animals, fungi, amoebozoans.

• Archaeplastida: Includes plants, green and red algae.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: Smaller, lack nucleus and membrane-bound organelles.

• Eukaryotes: Larger, have nucleus and organelles.

Organisms under Unikonta and Archaeplastida

• Unikonta: Animals, fungi, amoebas.

• Archaeplastida: Plants, green algae, red algae.

Chapter 17: Plants and Fungi

Plant Structure and Life Cycle

• Plant Cells: Parenchyma, collenchyma, sclerenchyma.

• Meristems: Regions of active cell division (apical, lateral).

• Organs: Roots, stems, leaves, flowers.

• Life Cycle: Alternation of generations between haploid gametophyte and diploid sporophyte.

Plant Evolution and Phylogeny

• Phylogenetic trees show evolutionary relationships among plant groups.

• Ferns vs. Mosses: Ferns have vascular tissue; mosses do not.

• Coal Formation: Formed during the Carboniferous period from ancient plant material.

Gymnosperms vs. Angiosperms

• Gymnosperms: Seeds not enclosed in fruit (e.g., pine trees).

• Angiosperms: Seeds enclosed in fruit (flowering plants).

Flower Structure and Reproduction

• Parts of Flower: Sepals, petals, stamens (anther, filament), carpels (stigma, style, ovary).

• Male Gametophyte: Pollen grain.

• Female Gametophyte: Embryo sac within ovule.

• Pollination: Transfer of pollen to stigma.

• Fertilization: Fusion of gametes.

• Cross-fertilization: Between different plants; Self-fertilization: Same plant.

• Ovule: Contains female gametophyte; Ovary: Develops into fruit.

• Pollen: Male gametophyte; Anther: Produces pollen.

• Seed Dispersal: Mechanisms include wind, water, animals.

Fungi: Life Cycle and Importance

• General Life Cycle: Includes haploid, dikaryotic (heterokaryotic), and diploid stages.

• Mushroom Life Cycle: Fruiting body produces spores.

• Heterokaryotic Phase: Cells contain two or more genetically distinct nuclei.

• Mycorrhiza: Symbiotic association between fungi and plant roots.

• Pathogenic Fungi: Can cause diseases in plants and animals (e.g., athlete's foot, ringworm).