UCONN Study Guide Full

Evidence of Evolution: Name and describe

Evidence of evolution includes:

• Direct Observation: Observing evolutionary changes directly (e.g., insect resistance to pesticides).
• Homology: Similar characteristics in related species due to common ancestry.
• Fossil Record: Remains or traces of past organisms, showing evolutionary changes over time.
• Biogeography: Geographic distribution of species reflecting evolutionary history.

Direct Observation

The method of studying organisms or ecosystems by watching them firsthand, without interference or relying on indirect evidence (like tracks, droppings, or modeling). Example: Insect becoming resistant to pesticides.

Homology

Characteristics in related species that have underlying similarities even though their function may differ, indicating shared ancestry.

Homologous Structures

Similar anatomy among common ancestors. Example: the bone structure in a whale's flipper and a bat's wing.

Embryology

Demonstrates similarities in early developmental stages among diverse organisms, hinting at shared ancestry.

Vestigial Organs

Structures with little or no current use, representing remnants of ancestral features. Ex: the human appendix.

Molecular Homologies

Similar DNA and amino acid sequences among different species, indicating common ancestry.

Convergent Evolution

The process where distantly related species can resemble one another due to similar environmental pressures.

Analogous Structures

Similar structures and function in similar environments, but arising independently without a recent common ancestor. Example: the wings of a bird and an insect.

Fossil Record

Fossils are the remains or traces of organisms from the past, found in sedimentary rocks. The fossil record shows evolutionary changes that occur over time and the origin of major new groups of organisms.

Biogeography

The geographic distribution of a species. Species in nearby geographic areas resemble each other. Continental drift (Pangaea) explains similarities on different continents. Endemic species are found at a certain geographic location and nowhere else.

Hardy-Weinberg Conditions

The conditions for Hardy-Weinberg equilibrium (no evolution) are: no genetic drift, random mating, no migration, no natural selection, no mutation, large population, stable allele frequency.

Hardy-Weinberg Equations

• p = frequency of dominant allele
• q = frequency of recessive allele
• p + q = 1
• Frequency of allele = number of copies of allele in population/Total number of copies of gene in population
• p^2 + 2pq + q^2 =1
  • p^2 = probability of homozygous dominant
  • 2pq = probability of heterozygous
  • q^2 = probability of homozygous recessive

Meiosis: Contribution to Genetic Variability

Meiosis is a form of cell division that reduces chromosome number by half, creating gametes. It contributes to genetic variability through independent assortment and crossing over during prophase I. Independent assortment allows for random distribution of maternal and paternal chromosomes into gametes.

Simple Punnett Squares

Tools used to predict the outcome of genetic crosses based on Mendelian inheritance (e.g., PpxGg). Illustrate the probability of offspring inheriting specific traits from parental genotypes. A monohybrid cross between two heterozygous pea plants (Tt x Tt) predicts a 3:1 phenotypic ratio. Dihybrid crosses can be represented by a 4x4 Punnett Square, predicting a 9:3:3:1 ratio for two traits.

Germ Mutations vs. Somatic Mutation

Germ Mutations:

• Occur in gametes (sperm or egg)
• Heritable – passed onto offspring
• Can affect every cell of the offspring’s body

Somatic Mutations:

• Occur in body cells (non-gametes)
• Not inherited – affects only the individual in which the mutation occurs
• Can lead to diseases like cancer, but won’t be passed onto offspring
  Only germ mutations affect future generation because present in the DNA of reproductive cells

Reinforcement

Reinforcement refers to the process where natural selection increases reproductive isolation between two populations. It occurs when hybrids between two populations have reduced fitness, and as a result, traits that prevent interbreeding become more common.

• Prevents the production of weak or sterile offspring
• Encourages divergence and speciation by strengthening prezygotic barriers (e.g., changes in mating behavior or timing)

Reproductive Isolation: Prezygotic mechanisms

Prezygotic isolation: Prevents mating or fertilization from occurring. Types include:

• Temporal isolation: Mating occurs at different times (seasons or time of day)
• Behavioral isolation: Different courtship behaviors or mating calls
• Mechanical isolation: Incompatible reproductive organs
• Gametic isolation: Sperm and egg can’t fuse (due to biochemical differences)
• Habitat isolation: Populations live in different environments

Reproductive Isolation: Postzygotic mechanisms

Postzygotic isolation: Occurs after fertilization, preventing viable or fertile offspring. Types include:

• Hybrid inviability: Embryo fails to develop properly or dies early
• Hybrid sterility: Offspring cannot reproduce (e.g., mule — horse x donkey)
• Hybrid breakdown: Offspring are fertile but subsequent generations are weak or sterile

Multicellularity

Transition from unicellular to multicellular organisms allowed for increased complexity an specialization of cells.

• Key evolutionary steps include cell adhesion, communication and differentiation among cells
• The evolution of multicellular algae and its impact on ecosystems
• Benefits of multicellularity include enhanced survival, resource acquisition and reproductive strategies
• Multicellularity is believed to have evolved independently in various lineages, including plants, animals and fungi

Endosymbiotic Theory

The endosymbiotic theory posits that eukaryotic cells originated from symbiotic relationships between prokaryotic cells.

• Mitochondria and chloroplasts are believed to have evolved from free-living bacteria that were engulfed by ancestral eukaryotic cells
• Evidence includes the presence of double membranes, circular DNA, and ribosomes similar to bacteria in these organelles

Phylogenetics

Phylogenetics is the study of evolutionary relationships among biological entities often using genetic data.

• Employs cladistics to classify organisms based on shared derived characteristics
• Phylogenetic trees visually represent these relationships, illustrating common ancestors and divergence points
• The tree of life shows the evolutionary pathways of major groups, including bacteria, archaea and eukaryotes

Asexual Reproduction

Produces offspring genetically identical to the parents. Types include:

• Binary fission: Single cell splits in two (bacteria)
• Budding: New organism grows off the parent (yeast)
• Fragmentation: Organism breaks into pieces that grow into new individuals (starfish)
• Spore Formation: Specialized cells (spores) are released and grow into new individual (fungi)
• Vegetative Propagation: New plants grow from roots, stems or leaves (potatoes)
• Parthenogenesis: Offspring develop from unfertilized eggs (insects)

Fungi: General Anatomy

Fungi anatomy includes:

• Hyphae: Thread-like filaments that make up the body
• Mycelium: Mass of hyphae; main vegetative part
• Spores: Reproduction units
• Fruiting Body: Visible part (like a mushroom) that produces spores

Fungi: Nutrient Acquisition

Heterotrophic decomposers—fungi secrete enzymes into their environment and absorb nutrients externally (extracellular digestion). Some are parasitic or mutualistic (mycorrhizae with plants roots).

Amniotic Egg

An egg with a protective shell and internal membranes (amniotic sac, yolk sac, etc.) that keep the embryo moist and nourished.

• Benefits:
  • Prevents desiccation (drying out)
  • Allows gas exchange while retaining moisture
  • Provides nutrients (yolk) and waste disposal (allantois)
  • Supports development outside water, enabling life in dry environments

Simplest Cellular Complexity: Order of Development

Order:

1: Multicellularity—simplest organisms to organize multiple cells (e.g., sponges)

2: Tissues—groups of cells with a specific function (e.g., cnidarians)

3: Bilateral symmetry—body plan with mirrored right and left sides (e.g., flatworms)

Vertebrate vs. Chordate

Chordate: Any animal with a notochord, dorsal nerve cord, pharyngeal slits, and post-anal tail at some stage. Includes vertebrates and some invertebrates (like lancelets and tunicates).

Vertebrate: A subgroup of chordates with a backbone or spinal column (e.g., fish, amphibians, reptiles, birds, mammals). All vertebrates are chordates, but not all chordates are vertebrates.

Evolution of Plants onto Land

The transition of plants from water to land required adaptations to prevent desiccation, support structures, and reproductive strategies.

• Key adaptations include the development of a cuticle, stomata, and vascular tissues.
• The evolution of mosses, ferns, and seed plants, each representing significant steps in terrestrial adaptation.
• These adaptations allowed plants to colonize diverse terrestrial environments, leading to increased biodiversity.

Alternation of Generations

Alternation of generations is a reproductive cycle in which organisms switch between haploid and diploid stages.

• This process allows for genetic diversity through sexual reproduction while maintaining a stable population through asexual reproduction.
• Increased adaptability to environmental changes and enhanced survival rates.

Photosynthesis: Purpose of Water

Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen. Water is essential as a reactant, providing electrons and protons during the light-dependent reactions. The light-dependent reactions occur in the thylakoid membranes, while the Calvin cycle takes place in the stroma of chloroplasts.

C3 Plants

• Initial CO₂ Fixation: Rubisco → 3-carbon compound
• CO₂ Capture Location: Same cell as Calvin Cycle
• Stomata Open: Day
• Climate: Cool, moist
• Examples: Rice, wheat, soybeans

C4 Plants

• Initial CO₂ Fixation: PEP carboxylase → 4-carbon
• CO₂ Capture Location: Mesophyll → Bundle sheath
• Stomata Open: Day
• Climate: Hot, sunny
• Examples: Corn, sugarcane

CAM Plants

• Initial CO₂ Fixation: PEP carboxylase at night → 4-carbon
• CO₂ Capture Location: Night (stored), day (Calvin Cycle)
• Stomata Open: Night
• Climate: Hot, dry (arid)
• Examples: Cactus, pineapple, agave

Bryophytes: Traits

• Mosses, liverworts, hornworts
  • No vascular tissue (xylem/phloem)
  • Moist environments
  • Dominant gametophyte stage
  • Require water for sperm to swim to egg

Tracheophytes: Traits

• Ferns, gymnosperms (conifers), angiosperms (flowering plants)
  • Has vascular tissue (xylem and phloem)
  • Dominant sporophyte age
  • Can grow tall and live in diverse environments

Xylem: Function

Transports water & minerals. Direction: One-way (roots → leaves). Cells: Tracheids, vessel elements. Mechanism: Transpiration pull, cohesion.

Phloem: Function

Transports sugars (food). Direction: Both directions. Cells: Sieve tubes, companion cells. Mechanism: Pressure-flow mechanism.

Primary Growth

Increases length of roots and shoots. Occurs at apical meristems (tips). Found in all plants.

Secondary Growth

Increases girth/width of stems and roots. Involves vascular cambium (produces xylem/phloem) and cork cambium. Found in woody plants (trees, shrubs).

Water Potential

Water moves from high water potential → low water potential. Influenced by:

• Solute concentration (more solutes = lower water potential)
• Pressure (turgor pressure increases potential)
  Water enters roots (osmosis) → xylem → up the plant (via cohesion-tension) → evaporates from leaves (transpiration).

Self-Fertilization

When a plant’s own pollen fertilizes its own ovule. Common in hermaphroditic flowers (ex. peas). Can reduce genetic diversity but ensures reproduction in low-pollinator environments.

Double Fertilization

One sperm fertilizes the egg → zygote (2n). Other sperm fuses with 2 polar nuclei → endosperm (3n). Result: Seed with embryo and food supply.

Auxin

Cell elongation, phototropism, apical dominance

Gibberellins

Stem elongation, seed germination, fruit growth

Cytokinins

Promote cell division, delay leaf aging, stimulate shoot formation

Abscisic Acid (ABA)

Inhibits growth, promotes seed dormancy, closes stomata during drought

Ethylene

Gas hormone; promotes fruit ripening, leaf drop

Biome Characteristics: Tundra

Cold, dry, low biodiversity, permafrost, mosses and lichens

Biome Characteristics: Taiga (Boreal Forest)

Cold with more precipitation, coniferous trees, bears, moose

Biome Characteristics: Temperate Forest

Four seasons, deciduous trees (like oaks), deer and foxes

Biome Characteristics: Grassland

Moderate rainfall, dominated by grasses, supports grazing animals like bison

Biome Characteristics: Desert

Very dry, extreme temperatures, plants like cacti, animals adapted to heat and water conservation

Biome Characteristics: Tropical Rainforest

Hot and wet year-round, high biodiversity, poor soil, dense canopy

Biome Characteristics: Savanna

Warm, seasonal rainfall, scattered trees, animals like elephants and lions

Exponential Growth

• J-shaped curve
  • Rapid population growth with no limits
  • Occurs when resources are unlimited

Logistic Growth

• S-shaped curve
  • Growth slows as population reaches carrying capacity
  • Limited by resources and environmental resistance

Food chains/Food Webs: Descriptive Vocab

Food chain: Linear flow of energy from producer to top consumer
Food web: complex network of interconnected food chains
Producer: Makes own food (via photosynthesis)
Primary Consumer: Eats produces (herbivore)
Secondary Consumer: Eats primary consumers
Tertiary consumer: Eats secondary consumers; often top predator
Decomposer: Breaks down dead matter; recycles nutrients (ex. Fungi, bacteria)
Energy flow: Only ~10% of energy transfers to next level; rest lost as heat

Trophic Levels

Producers: base level, make food from sunlight
Primary Consumers: Eat producers (herbivores)
Secondary Consumers: Eat herbivores (carnivores/omnivores)
Tertiary Consumers: Eat other carnivores; top of the food chain
Decomposers: Break down all levels’ waste and dead matter

Nutrient Cycling: Water Cycle

Includes evaporation, condensation, precipitation, runoff, infiltration, transpiration. Moves water through air, land and organisms.

Nutrient Cycling: Carbon Cycle

Photosynthesis removes carbon dioxide; respiration and combustion return it. Carbon moves through atmosphere, organisms and fossil fuels.

Nutrient Cycling: Nitrogen Cycle

Nitrogen fixation: converts N_2 gas into ammonia (by bacteria)
Nitrification: Ammonia → nitrites → nitrates
Assimilation: Plants absorb nitrates
Decomposition: Returns nitrogen to soil
Denitrification: Release nitrogen gas back to the atmosphere

Symbiotic Relationships

Mutualism: Both species benefit (ex. Bees and flowers)
Commensalism: One benefits, the other is unaffected (ex. Barnacles on whales)
Parasitism: One benefits, one is harmed (ex. Fleas on dogs)

Density-Dependent Limiting Factors

Effect increases with population size:

• Competition for resources
• Disease spread
• Predation
• Food or space shortage

Density-Independent Limiting Factors

Affect population regardless of size:

• Natural disasters (floods, fires)

• Climate extremes

• Human activities (pollution, habitat destruction)