unit 2

Gnathostomes

Jawed fishes, which include all vertebrates with jaws.

Pharyngeal slits

Structures used only for gas exchange in fish.

Lateral line system

Sensory organ in fishes used for detecting water movement.

Gill arches

Bones or cartilage between gill slits modified into jaws.

Chondrichthyes

Class of cartilaginous fishes, including sharks and rays.

Osteichthyes

Class of bony fishes, which can be ray-finned or lobe-finned.

Placoderms

Extinct armored jawed fishes that existed around 440 million years ago.

Ray-finned fishes

Largest group of bony fishes characterized by bony rays supporting their fins.

Lobe-finned fishes

Fishes with sturdy, rod-shaped bones in their fins, important for the evolution of terrestrial vertebrates.

Swim bladder

An air-filled organ in bony fishes that helps maintain buoyancy.

Operculum

Bony flap that covers and protects gills in bony fishes.

Cartilaginous skeleton

Skeleton made of cartilage, as seen in sharks and rays.

Placoid scales

Rough, tooth-like scales found on cartilaginous fishes.

Spiral valve

Modifies the intestine for nutrient absorption in cartilaginous fishes.

Countercurrent exchange

A mechanism that maximizes O₂ uptake in fish gills.

Fecundity

The reproductive capacity of an organism, measured by the number of offspring per female.

Survivorship curves

Graphs representing the number of individuals surviving at each age interval.

Type I survivorship curve

High survival rate throughout life with a rapid decline at old age.

Type II survivorship curve

Constant mortality rate throughout the lifespan.

Type III survivorship curve

High early mortality with survivors living longer.

Semelparity

Reproductive strategy in which organisms reproduce once and often die afterward.

Iteroparity

Reproductive strategy in which organisms reproduce multiple times during their life.

Density-dependent factors

Biological factors that regulate population size based on density, like competition and disease.

Density-independent factors

Environmental factors that affect population size regardless of density, like natural disasters.

Optimal foraging theory

The theory that animals maximize their energy gain while foraging.

Altruism

Behaviors that reduce individual fitness but help others, such as alarm calls.

Kin selection

A form of natural selection favoring behaviors that enhance the reproductive success of relatives.

Biotic factors

Living components of an ecosystem, including species interactions and competition.

Abiotic factors

Nonliving components of an ecosystem, such as climate, soil, and water availability.

Eutrophication

Process by which excess nutrients in water bodies lead to algal blooms and oxygen depletion.

Carrying capacity (K)

The maximum population size that an environment can sustain indefinitely.

Biogeochemical cycles

Nutrient cycles that describe the flow of chemical substances through the biotic and abiotic components of the ecosystem.

NPP (Net Primary Production)

The amount of energy or biomass produced by photosynthetic organisms available for consumption after subtracting energy lost through respiration.

GPP (Gross Primary Production)

Total energy captured by photosynthesis before losses from respiration.

NEP (Net Ecosystem Production)

Total energy stored in an ecosystem, taking into account both producers and consumers.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

Phosphatases and chelating agents

Enzymes and compounds used by plants to enhance the solubility and uptake of nutrients.

Trophic levels

Levels in an ecosystem comprising the organisms that share the same function in the food chain.

Foundation species

Species that have a strong role in structuring a community; they provide habitat and resources.

Keystone species

Species that play a critical role in maintaining the structure of an ecological community.

Hollow bones in birds

Adaptations that reduce weight for flight without sacrificing strength.

Aposematic coloration

Bright coloring in animals intended to warn predators of toxicity.

Müllerian mimicry

A form of mimicry where two or more unpalatable species evolve to resemble each other.

Batesian mimicry

A form of mimicry where a harmless species resembles a harmful one.

Chemical warfare

Use of toxins by predators to subdue prey or by prey to deter predators.

Community structure

The composition and organization of a community, including species richness and abundance.

Disturbance

A temporary change in environmental conditions that causes a pronounced change in an ecosystem.

Intermediate Disturbance Hypothesis

The concept that moderate levels of disturbance can enhance species diversity.

Primary succession

Ecological succession that begins in barren areas with no soil.

Secondary succession

Succession following a disturbance that destroys a community without destroying the soil.

Latitudinal diversity gradient

The increase in species diversity observed as one moves from the poles to the tropics.

Trophic efficiency

The percentage of energy transferred from one trophic level to the next.

Community resilience

The ability of a community to withstand disturbances and return to its original state.

Successful invasive species

Species that thrive in new environments due to lack of natural predators or competitors.

Metapopulations

Groups of populations that are separated by space but consist of the same species.

Interspecific competition

Competition between different species for the same resources in an ecosystem.

Intraspecific competition

Competition among members of the same species for limited resources.

Fecundity schedule

A table of the age-specific fertility rates of a population.