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BIO 1108: Evolution, History of Life, Plant Biology, and Ecology – Study Guide

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Evolution

Evidence of Evolution

Multiple lines of evidence support the theory of evolution, demonstrating how species change over time and share common ancestry.

  • Fossil Record: Shows chronological changes in species and the existence of transitional forms.

  • Comparative Anatomy:

    • Homologous Structures: Structures with a common evolutionary origin but different functions (e.g., human arm and whale flipper).

    • Analogous Structures: Structures with similar functions but different evolutionary origins (e.g., wings of birds and insects), indicating convergent evolution.

    • Vestigial Structures: Reduced or nonfunctional traits inherited from ancestors (e.g., whale pelvis).

  • Molecular Evidence: Similarities in DNA and protein sequences indicate evolutionary relationships.

  • Biogeography: The geographic distribution of species supports patterns of evolution and speciation.

Hardy-Weinberg Principle

The Hardy-Weinberg equilibrium provides a mathematical model to study genetic variation in populations and determine if evolution is occurring.

  • Purpose: To determine if a population is evolving by comparing observed and expected genotype frequencies.

  • Equations:

    where p = frequency of dominant allele, q = frequency of recessive allele.

  • Conditions for Equilibrium: (All must be met)

    1. Large population size

    2. No mutations

    3. No migration (gene flow)

    4. Random mating

    5. No natural selection

Meiosis and Genetic Variation

Meiosis increases genetic diversity in sexually reproducing organisms.

  • Crossing Over (Prophase I): Homologous chromosomes exchange genetic material, creating new allele combinations.

  • Independent Assortment: Random alignment of homologous chromosomes during metaphase I leads to varied gametes.

  • Random Fertilization: Any sperm can fertilize any egg, further increasing genetic diversity.

Mendelian Genetics and Punnett Squares

Punnett squares are used to predict the genotypes and phenotypes of offspring from genetic crosses.

  • Example: Aa x Aa cross yields a 3:1 phenotype ratio (dominant:recessive).

Mutations: Germline vs. Somatic

  • Germline Mutations: Occur in gametes; heritable and can be passed to offspring.

  • Somatic Mutations: Occur in body cells; not inherited (e.g., mutations leading to cancer).

Reinforcement and Reproductive Isolation

Reinforcement strengthens reproductive barriers, preventing the formation of unfit hybrids.

  • Prezygotic Barriers (before fertilization):

    • Temporal isolation

    • Mechanical isolation

    • Behavioral isolation

    • Habitat isolation

    • Gametic isolation

  • Postzygotic Barriers (after fertilization):

    • Reduced hybrid viability

    • Reduced hybrid fertility

    • Hybrid breakdown

History of Life

Multicellularity

The evolution from unicellular to multicellular organisms allowed for increased size, efficiency, and division of labor.

  • Cells specialized into tissues, organs, and organ systems.

Endosymbiotic Theory

This theory explains the origin of mitochondria and chloroplasts as formerly free-living bacteria engulfed by ancestral eukaryotic cells.

  • Evidence: Presence of their own DNA, double membranes, and ribosomes similar to bacteria.

Phylogenetics

Phylogenetics classifies organisms based on evolutionary relationships, often using cladograms and shared derived traits.

Asexual Reproduction

Asexual reproduction produces offspring without the fusion of gametes, resulting in low genetic diversity but rapid population growth.

  • Types: Binary fission, budding, fragmentation, parthenogenesis.

Fungi: Anatomy and Nutrition

  • Anatomy: Composed of hyphae (filaments) forming a mycelium; cell walls made of chitin.

  • Nutrition: Absorptive heterotrophs; secrete enzymes externally to digest food.

Amniotic Egg

The amniotic egg is a key adaptation for terrestrial life, protecting the embryo from desiccation and allowing reproduction away from water.

Evolution of Complexity

Traits evolved in the following order:

  1. Multicellularity

  2. Tissues

  3. Bilateral symmetry

Chordates vs. Vertebrates

  • Chordates: Animals with a notochord, dorsal nerve cord, pharyngeal slits, and post-anal tail.

  • Vertebrates: Chordates that possess a backbone.

Plant Form and Function

Evolution of Plants onto Land

Plants faced several challenges in colonizing land and evolved adaptations to overcome them.

  • Water loss: Development of a waxy cuticle.

  • Support: Lignin in cell walls for structural support.

  • Transport: Vascular tissues (xylem and phloem).

  • Reproduction: Pollen and seeds for dispersal without water.

Alternation of Generations

Plants alternate between haploid (gametophyte) and diploid (sporophyte) generations, increasing genetic diversity.

  • Gametophyte (n): Produces gametes.

  • Sporophyte (2n): Produces spores.

Photosynthesis: Role of Water and Locations

  • Water: Provides electrons and protons; releases O2 as a byproduct.

  • Light Reactions: Occur in the thylakoid membrane.

  • Calvin Cycle: Occurs in the stroma of the chloroplast.

C3, C4, and CAM Plants

Plants have evolved different photosynthetic pathways to adapt to their environments.

Type

Key Feature

Example

C3

Standard pathway; most efficient in cool, moist climates

wheat, rice

C4

Spatial separation of steps; adapted to hot climates

corn

CAM

Temporal separation of steps; adapted to dry climates

cactus

Bryophytes and Tracheophytes

  • Bryophytes: Nonvascular plants; require water for reproduction (e.g., mosses).

  • Tracheophytes: Vascular plants with xylem and phloem.

Xylem and Phloem

Tissue

Function

Cell Type

Xylem

Transports water and minerals upward

Dead cells

Phloem

Transports sugars in both directions

Living cells

Primary vs. Secondary Growth

  • Primary Growth: Increases length of stems and roots.

  • Secondary Growth: Increases width (girth) of stems and roots.

Water Potential and Movement

Water moves through plants from regions of high to low water potential, driven by solute concentration and pressure.

Self-Fertilization and Double Fertilization

  • Self-Fertilization: The same plant provides both sperm and egg; ensures reproduction but reduces genetic diversity.

  • Double Fertilization: One sperm fertilizes the egg (zygote), another fertilizes the central cell (endosperm, nutrient tissue).

Plant Hormones

Hormone

Main Function

Auxins

Cell elongation

Gibberellins

Stem growth, seed germination

Cytokinins

Cell division

Ethylene

Fruit ripening

Abscisic acid

Stress response, dormancy

Ecology

Biome Characteristics

Biomes are large ecological areas defined by climate, vegetation, and latitude.

  • Examples: tundra, desert, rainforest.

Population Growth Models

  • Exponential Growth: Occurs with unlimited resources; produces a J-shaped curve.

  • Logistic Growth: Limited by carrying capacity; produces an S-shaped curve.

Food Chains and Food Webs

Food chains show linear energy flow; food webs illustrate interconnected feeding relationships.

  • Trophic Levels:

    1. Producer

    2. Primary Consumer

    3. Secondary Consumer

    4. Tertiary Consumer

  • Only about 10% of energy is transferred between trophic levels.

Nutrient Cycling

Cycle

Main Processes

Water

Evaporation, precipitation

Carbon

Photosynthesis, respiration, combustion

Nitrogen

Fixation, nitrification, denitrification

Symbiotic Relationships

  • Mutualism: Both species benefit.

  • Commensalism: One benefits, the other is unaffected.

  • Parasitism: One benefits, one is harmed.

Limiting Factors

  • Density-Dependent: Effects increase with population density (e.g., disease, competition).

  • Density-Independent: Effects are unrelated to population density (e.g., weather, natural disasters).

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