Honors Biology Final Study Guide: Key Concepts and Definitions

Chapter 27: Reproduction and Embryonic Development

Key Terms and Structures

• Spermatogenesis: The process by which sperm cells are produced in the testes through meiosis. Example: In humans, spermatogenesis results in four haploid sperm cells from each diploid spermatogonium.

• Oogenesis: The process of egg (ovum) formation in the ovaries, involving meiosis. Example: In humans, oogenesis produces one mature ovum and three polar bodies from each primary oocyte.

• Oocyte: An immature egg cell undergoing development in the ovary.

• Corpus luteum: A temporary endocrine structure in the ovary formed from the follicle after ovulation; secretes progesterone and estrogen.

• Endometrium: The inner lining of the uterus, which thickens in preparation for possible implantation of an embryo.

• Ovary: Female gonad that produces eggs and hormones (estrogen and progesterone).

• Oviduct (Fallopian tube): Tube through which an ovulated egg travels from the ovary to the uterus; site of fertilization.

• Epididymis: Coiled tube where sperm mature and are stored in males.

• Seminal vesicle: Gland that secretes fluid rich in sugars to nourish sperm; contributes to semen.

• Vas deferens: Tube that transports sperm from the epididymis to the urethra.

• Prostate: Gland that adds alkaline fluid to semen, enhancing sperm motility and viability.

• FSH (Follicle-Stimulating Hormone): Hormone that stimulates gamete production in both sexes; in females, stimulates follicle growth; in males, stimulates spermatogenesis.

• LH (Luteinizing Hormone): Hormone that triggers ovulation in females and stimulates testosterone production in males.

• Progesterone: Hormone produced by the corpus luteum; maintains the endometrium for pregnancy.

• Estrogen: Hormone produced by the ovaries; promotes development of female secondary sexual characteristics and regulates the menstrual cycle.

Understanding Reproductive Systems and Processes

• Structures of the Female Reproductive System: Includes the ovaries, oviducts, uterus, endometrium, cervix, and vagina.

• Structures of the Male Reproductive System: Includes the testes, epididymis, vas deferens, seminal vesicles, prostate, and penis.

• Hormones in Ovulatory and Menstrual Cycles: FSH and LH regulate follicle development and ovulation; estrogen and progesterone regulate the uterine cycle.

• Meiosis in Gamete Production: Spermatogenesis produces four sperm per precursor cell; oogenesis produces one ovum and polar bodies. Oogenesis is discontinuous and pauses at certain stages, while spermatogenesis is continuous after puberty.

Chapter 9: Patterns of Inheritance

Key Terms

• Genotype: The genetic makeup of an organism (e.g., AA, Aa, aa).

• Phenotype: The observable traits of an organism (e.g., purple flowers, white flowers).

• Allele: Alternative forms of a gene found at the same locus (e.g., A and a).

• Locus: The specific location of a gene on a chromosome.

• Recessive trait: Trait expressed only when two recessive alleles are present (e.g., aa).

• Dominant trait: Trait expressed when at least one dominant allele is present (e.g., AA or Aa).

Understanding Mendelian Genetics

• Punnett Square: A diagram used to predict the genotype and phenotype ratios of offspring from a genetic cross.

• Dihybrid Cross: A cross between individuals differing in two traits (e.g., RrYy x RrYy).

• Probability of Inheritance: Calculated using Punnett squares and the rules of probability. For independent traits, multiply the probabilities of each trait.

Chapter 10: Molecular Biology of the Gene

Key Terms

• Ligase: Enzyme that joins DNA fragments together by forming phosphodiester bonds.

• Helicase: Enzyme that unwinds the DNA double helix during replication.

• DNA polymerase: Enzyme that synthesizes new DNA strands by adding nucleotides to a template strand.

• Primase: Enzyme that synthesizes short RNA primers needed for DNA polymerase to start replication.

• Codon: A sequence of three nucleotides in mRNA that codes for a specific amino acid.

• tRNA (transfer RNA): RNA molecule that brings amino acids to the ribosome during translation.

• Transcription: The process of copying a gene's DNA sequence into mRNA.

• Translation: The process where ribosomes synthesize proteins using the mRNA sequence.

• PCR (Polymerase Chain Reaction): Technique to amplify specific DNA sequences in vitro.

Understanding Genetic Information Flow and Techniques

• Flow of Genetic Information: DNA → RNA → Protein (the central dogma).

• Steps of DNA Replication: Initiation (unwinding), elongation (synthesis of new strands), termination.

• Roles of Proteins in Replication: Helicase unwinds DNA, primase lays primers, DNA polymerase synthesizes new DNA, ligase joins fragments.

• PCR Reaction: Involves denaturation (heating to separate strands), annealing (cooling to allow primers to bind), and extension (DNA synthesis by Taq polymerase).

• Applications of PCR: Genetic testing, forensic analysis, disease diagnosis.

• Designing a PCR Experiment: Requires template DNA, primers, nucleotides, buffer, and Taq polymerase.

• Interpreting PCR Results: Gel electrophoresis separates DNA fragments by size; bands indicate presence/absence of target sequences.

Chapter 13: How Populations Evolve

Key Terms

• Evolutionary tree: Diagram showing evolutionary relationships among species.

• Mutation: A change in DNA sequence; source of genetic variation.

• Gene pool: All the alleles present in a population.

• Microevolution: Small-scale changes in allele frequencies within a population.

• Gene flow: Movement of alleles between populations.

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

• Bottleneck effect: Sharp reduction in population size, reducing genetic diversity.

• Founder effect: Genetic drift when a few individuals colonize a new area.

• Relative fitness: An individual's contribution to the next generation compared to others.

• Homologous structures: Anatomical features with similar origin but different functions (e.g., human arm and whale flipper).

• Disruptive selection: Favors extreme phenotypes over intermediates.

• Directional selection: Favors one extreme phenotype.

• Stabilizing selection: Favors intermediate phenotypes.

• Intrasexual selection: Competition among individuals of the same sex for mates.

Understanding Evolutionary Mechanisms

• Fossils: Provide evidence for evolution and help track evolutionary changes over time.

• Artificial Selection: Human-driven selection of desirable traits (e.g., dog breeding).

• Natural Selection: Differential survival and reproduction due to environmental pressures.

• Hardy-Weinberg Equilibrium Conditions: No mutation, random mating, no gene flow, infinite population size, no selection.

• Antibiotic Resistance: Arises through mutation and selection; can be slowed by proper antibiotic use.

Chapter 14: The Origin of Species

Key Terms

• Speciation: Formation of new species.

• Allopatric speciation: Speciation due to geographic isolation.

• Sympatric speciation: Speciation without geographic isolation.

• Adaptive radiation: Rapid evolution of many species from a common ancestor.

• Hybrid zones: Regions where different species meet and mate, producing hybrids.

• Punctuated equilibrium: Evolutionary pattern with long periods of stability interrupted by brief periods of rapid change.

• Gradual evolution: Slow, steady accumulation of changes.

• Prezygotic Barriers: Prevent mating or fertilization (habitat, temporal, behavioral, mechanical, gametic).

• Postzygotic Barriers: Prevent hybrid offspring from developing into viable, fertile adults (hybrid breakdown, reduced hybrid fertility, reduced hybrid viability).

Understanding Species Concepts and Isolation

• Reproductive Isolation: Mechanisms that prevent gene flow between species.

• Biological Species Concept: Defines species as groups of interbreeding populations reproductively isolated from others.

• Morphological Species Concept: Defines species by structural features.

• Ecological Species Concept: Defines species by ecological niche.

• Phylogenetic Species Concept: Defines species as the smallest group sharing a common ancestor.

Chapter 36: Population Ecology

Key Terms

• Ecology: Study of interactions between organisms and their environment.

• Biotic factors: Living components of an environment (e.g., plants, animals).

• Abiotic factors: Nonliving components (e.g., temperature, water, sunlight).

• Habitat: The natural environment where an organism lives.

• Organism: An individual living thing.

• Population: Group of individuals of the same species in an area.

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

• Ecosystem: Community plus abiotic factors.

• Landscape: Mosaic of connected ecosystems.

• Biosphere: All ecosystems on Earth.

• Population ecology: Study of population dynamics and regulation.

• Dispersion Patterns: Clumped (grouped), uniform (evenly spaced), random (unpredictable).

• Limiting factors: Environmental factors that restrict population growth.

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

• Ecological footprint: Measure of human demand on Earth's ecosystems.

Understanding Population Dynamics

• Survivorship Curves: Graphs showing the proportion of individuals surviving at each age.

• Population Growth Models: Exponential growth (J-shaped, unlimited resources), logistic growth (S-shaped, limited by carrying capacity).

• K-selection: Traits favoring survival in stable environments (few offspring, high parental care).

• r-selection: Traits favoring rapid reproduction in unpredictable environments (many offspring, low parental care).

• Age Structure Pyramids: Show distribution of ages in a population; can predict growth trends.

• Density-Independent Factors: Affect populations regardless of size (e.g., weather, disasters).

• Density-Dependent Factors: Impact increases with population density (e.g., competition, disease).

• Population Growth Rate: $r = b - d$ (birth rate minus death rate).

• Predator-Prey Relationships: Can cause population cycles (boom and bust).

• Sustainability and Resource Management: Practices like regulated hunting and fishing maintain populations and resources.

Chapter 37: Communities and Ecosystems

Key Terms

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

• Ecological Succession: Sequence of changes in a community over time. Primary succession: Begins on bare substrate; Secondary succession: Follows disturbance in an existing community.

• Mutualism: Both species benefit (e.g., bees and flowers).

• Herbivory: Animals eat plants.

• Predation: One organism kills and eats another.

• Parasitism: One organism benefits, the other is harmed.

• Interspecific competition: Different species compete for the same resource.

• Primary producer: Autotrophs (e.g., plants) that produce energy-rich compounds.

• Primary consumer: Herbivores that eat producers.

• Secondary consumer: Carnivores that eat herbivores.

• Tertiary consumer: Carnivores that eat other carnivores.

• Quaternary consumer: Top predators in a food chain.

• Detritivore: Organisms that feed on dead organic matter (e.g., earthworms).

• Ecological niche: Role and position a species has in its environment.

• Primary production: Amount of light energy converted to chemical energy by producers.

• Biological magnification: Increase in concentration of toxins up the food chain.

Understanding Community Structure and Energy Flow

• Trophic Structure: Feeding relationships among organisms in a community.

• Food Webs: Complex networks of feeding interactions.

• Energy Loss: Only about 10% of energy is transferred from one trophic level to the next; most is lost as heat.

Chapter 38: Conservation Biology

Key Terms

• Biodiversity: Variety of life in all its forms. Types: Genetic, species, and ecosystem diversity.

• Species richness: Number of different species in an area.

• Extinction: Loss of all individuals of a species.

• Keystone species: Species with a disproportionately large effect on its ecosystem.

• Phenotypic plasticity: Ability of an organism to change its phenotype in response to environmental conditions.

• Invasive species: Non-native species that spread rapidly and harm native species and ecosystems.

• Biodiversity hotspot: Area with high levels of endemic species and significant habitat loss.

• Endemic species: Species found only in a specific geographic area.

Understanding Conservation Issues

• Threats to Biodiversity: Habitat destruction, invasive species, pollution, overexploitation, climate change.

• Climate Change and Global Warming: Caused by increased greenhouse gases (e.g., CO2); leads to rising temperatures, altered habitats, and species loss.

Sample Table: Types of Selection (Chapter 13)

Type of Selection	Description	Example
Stabilizing	Favors intermediate phenotypes	Human birth weight
Directional	Favors one extreme phenotype	Antibiotic resistance in bacteria
Disruptive	Favors both extremes over intermediates	Beak size in African finches

Sample Table: Prezygotic vs. Postzygotic Barriers (Chapter 14)

Barrier Type	Examples	Description
Prezygotic	Habitat, Temporal, Behavioral, Mechanical, Gametic	Prevent mating or fertilization
Postzygotic	Hybrid breakdown, Reduced hybrid fertility, Reduced hybrid viability	Prevent hybrid offspring from becoming viable, fertile adults

Sample Table: Population Growth Models (Chapter 36)

Model	Equation	Graph Shape
Exponential	$\frac{dN}{dt} = rN$	J-shaped
Logistic	$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$	S-shaped