BIO101 Test 1 Study Notes (Lectures 1–7)

Comprehensive vocabulary flashcards covering foundational biology concepts from Lectures 1 through 7, including biological hierarchy, evolutionary theory, population genetics, speciation, origin of life, and plant adaptations.

Tissue

A group of specialized cells working together to perform a specific function (e.g., skin, muscle, bone, blood).

Organ

A structure composed of different tissues performing a distinct function (e.g., the stomach, which combines muscle and a lining that secretes digestive juice).

Organ system

A cooperative group of organs functioning together to carry out major bodily processes (e.g., the digestive system).

Population

A group of individuals of the same species living in the same geographic area at the same time.

Community

All the different populations of different species interacting within a specific area.

Ecosystem

A biological community of interacting organisms together with the abiotic (nonliving) components of their environment.

Biosphere

The global ecological system integrating all living beings and their relationships; all ecosystems on Earth combined.

Biotic factors

The living components that influence an ecological system (e.g., plants, insects, fungi).

Abiotic factors

The nonliving physical and chemical components of an environment (e.g., temperature, pH, humidity, salinity, sunlight).

Producers (autotrophs)

Organisms that make their own food from simple raw materials using light or chemical energy (e.g., plants, algae).

Consumers (heterotrophs)

Organisms that depend directly or indirectly on producers for food and energy.

Decomposers

Heterotrophic organisms that break down dead organic matter and play a key role in recycling nutrients (e.g., bacteria, fungi).

Cell

The simplest self-replicating entity that can exist as an independent unit of life.

Prokaryotic cell

A typically small ($\sim 1/10$ the size of eukaryotic cells), mostly unicellular cell lacking a membrane-bound nucleus (DNA resides in a nucleoid) and membrane-bound organelles (e.g., bacteria, archaea).

Eukaryotic cell

A larger unicellular or multicellular cell containing a membrane-bound nucleus and specialized membrane-bound organelles (e.g., plants, animals, fungi, protists).

Genome

An organism's complete set of DNA, containing all of its genes and heritable information.

Evolution

Descent with modification; the process by which modern organisms descended from ancestral species, driven primarily by natural selection.

Scala naturae

Aristotle's classical concept that all life forms are fixed, permanent, and arranged linearly on a ladder of increasing complexity.

Gradualism (Hutton and Lyell)

The geological principle that Earth's surface changes via slow, continuous processes still operating today, implying Earth is very old and allowing time for biological evolution.

Inheritance of acquired characteristics

Lamarck's unsupported hypothesis that modifications acquired by an organism through use or disuse during its lifetime can be inherited by offspring.

Natural selection

A process in which individuals with favorable heritable traits survive and reproduce at higher rates than other individuals, causing adaptive traits to accumulate over generations.

Homologous structures

Anatomical structures in different species that share a common ancestral skeletal arrangement despite differing in present function (evidence of divergent evolution).

Vestigial structures

Remnants of functional features found in ancestral species that have lost most or all of their original function in descendant species (e.g., pelvis/hind limb bones in whales and snakes).

Convergent evolution

The independent evolution of similar (analogous/homoplastic) features in distantly related lineages due to adaptation to similar environmental pressures.

Biogeography

The scientific study of the geographic distributions of species, showing that closely related species are often found in nearby geographical areas.

Microevolution

A change in allele frequencies within a population over successive generations (evolution below the species level).

Gene pool

The aggregate of all copies of every type of allele at all loci in all individuals in a population.

Hardy-Weinberg equilibrium

The state of a non-evolving population where allele and genotype frequencies remain constant across generations under five conditions: no mutations, random mating, no natural selection, extremely large population size, and no gene flow.

Directional selection

A mode of natural selection that shifts the overall makeup of the population by favoring individuals at one extreme of the phenotypic distribution.

Disruptive selection

A mode of natural selection that favors variants at both ends of the phenotypic distribution over intermediate phenotypes.

Stabilizing selection

A mode of natural selection that acts against extreme phenotypes, favoring intermediate variants and maintaining status quo.

Genetic drift

Chance events causing unpredictable fluctuations in allele frequencies from one generation to the next, exerting its strongest effects in small populations.

Bottleneck effect

A drastic reduction in population size caused by an environmental disaster (flood, fire, earthquake), leaving a small surviving sample that randomly underrepresents original allele diversity.

Founder effect

A type of genetic drift occurring when a few individuals colonize a new habitat or become isolated from a larger population, carrying only a fraction of the original genetic variation.

Gene flow

The transfer of alleles into or out of a population due to the migration of fertile individuals or gametes, reducing genetic differences between populations.

Sexual selection

A form of selection where individuals with certain inherited characteristics are more likely than others to obtain mates, often driving sexual dimorphism.

Macroevolution

Broad evolutionary patterns and changes occurring above the species level over deep time, linked to microevolution through speciation.

Biological species concept

Defines a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring (cannot be applied to asexual organisms or fossils).

Morphological species concept

Distinguishes and classifies species based on body shape and unique structural features, relying on subjective criteria.

Ecological species concept

Identifies species based on their ecological niche—the sum of their interactions, behaviors, and environmental roles—and applies to both sexual and asexual organisms.

Phylogenetic species concept

Defines a species as the smallest group of individuals that share a common ancestor on a phylogenetic tree, established via molecular or sequence data.

Prezygotic barriers

Reproductive isolation mechanisms that impede mating or prevent fertilization from occurring between species (habitat, temporal, behavioral, mechanical, and gametic isolation).

Postzygotic barriers

Reproductive isolation mechanisms that operate after fertilization to prevent hybrid zygotes from developing into viable, fertile adults (reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown).

Allopatric speciation

The formation of new species in populations that are geographically separated from one another, restricting gene flow.

Sympatric speciation

The formation of new species in populations that inhabit the same geographic region, driven by polyploidy, habitat differentiation, or sexual selection.

Adaptive radiation

A period of rapid evolutionary change in which an ancestral species diversifies into many diverse descendant species to exploit newly available ecological opportunities (adaptive zones).

Monophyletic group (clade)

A taxonomic grouping consisting of an ancestral species and all of its evolutionary descendants.

Paraphyletic group

A taxonomic group consisting of an ancestral species and only some, but not all, of its evolutionary descendants.

Oparin-Haldane hypothesis

The 1920s proposal that Earth's early reducing atmosphere, combined with intense energy sources, drove the abiotic chemical synthesis of organic molecules into a 'primordial soup.'

Protocells (protobionts)

Abiotically produced, membrane-bound spherical droplets that maintain an internal chemical environment and exhibit basic metabolic and replicative properties.

Ribozymes

RNA molecules that function as catalytic enzymes, capable of catalyzing reactions such as self-replication.

Stromatolites

Layered rock formations produced when cyanobacteria trap and bind mineral sediments; the oldest fossils ($\sim 3.5$ billion years old) documenting early prokaryotic life.

Endosymbiont theory

The theory that eukaryotic organelles (mitochondria and chloroplasts) originated as small, free-living aerobic or photosynthetic prokaryotes that were engulfed by ancestral host cells.

Photoautotrophs

Organisms that utilize sunlight energy to fix carbon dioxide into organic matter through the process of photosynthesis (e.g., plants, algae, cyanobacteria).

Chemoautotrophs

Organisms that obtain metabolic energy by oxidizing inorganic chemical compounds (such as $H_2S$) to fix carbon via chemosynthesis (e.g., deep-sea vent bacteria and archaea).

Stomata

Microscopic pores on leaf surfaces flanked by pairs of guard cells that open and close to regulate photosynthetic gas exchange and transpiration.

Photorespiration

A metabolic pathway where rubisco binds $O_2$ instead of $CO_2$, consuming ATP and releasing carbon dioxide without yielding sugar, thereby reducing photosynthetic efficiency in hot, dry conditions.

C4 photosynthesis

A photosynthetic pathway that spatializes carbon fixation by capturing $CO_2$ with PEP carboxylase into a 4-carbon compound in mesophyll cells before transferring it to deeper bundle-sheath cells for rubisco.

CAM photosynthesis

Crassulacean Acid Metabolism; a photosynthetic pathway that temporally separates carbon fixation by opening stomata exclusively at night to store $CO_2$ as an organic acid, keeping stomata closed during hot days to prevent water loss.

Root:shoot ratio

The ratio measuring plant resource allocation between root biomass and shoot biomass, where a ratio greater than 1 ($> 1$) indicates higher investment in roots to acquire scarce water.