3 big topics on biology regents

Cell Division

The process by which a growing cell divides to form two daughter cells before it becomes too large.

Daughter Cells

The two cells formed after cell division, each receiving a complete set of genetic information.

Surface Area to Volume Ratio

The relationship between the surface area of a cell's membrane and its internal volume; a higher ratio allows for more efficient nutrient and waste exchange.

Chromosomes

Thread-like structures made of DNA and proteins (histones) that carry the cell's coded genetic information.

Chromatin

The combination of DNA and protein that makes up chromosomes.

Histones

Proteins that DNA wraps around to form chromatin.

Sister Chromatids

Two identical parts of a replicated chromosome.

Centromere

The area where sister chromatids are attached to each other.

Diploid (2n)

A cell containing two sets of chromosomes (one from each parent).

Haploid (n)

A cell containing only a single set of chromosomes.

Cell Cycle

The series of events that cells go through as they grow and divide.

Interphase

The period of growth and preparation for division, consisting of G1, S, and G2 phases.

G1 Phase

Period of cell growth.

S Phase

Period of DNA replication.

G2 Phase

Period of preparation for mitosis (organelles produced).

M Phase

The phase of cell division, which includes mitosis and cytokinesis.

Mitosis

The division of the cell nucleus.

Prophase

The first and longest phase of mitosis; chromosomes become visible, centrioles separate, and the spindle forms.

Metaphase

Chromosomes line up across the center of the cell; microtubules connect the centromere to the poles.

Anaphase

Sister chromatids separate into individual chromosomes and move apart.

Telophase

Chromosomes gather at opposite ends of the cell and lose their distinct shape; two new nuclear envelopes form.

Cytokinesis

The division of the cytoplasm itself.

Cleavage Furrow

The pinching of the cell membrane in animal cells during cytokinesis.

Cell Plate

Structure that forms midway between divided nuclei in plant cells, eventually becoming the cell wall.

Spindle

Fanlike microtubule structure that helps separate the chromosomes.

Centrioles

Two tiny structures located in the cytoplasm near the nuclear envelope that help organize the spindle.

Cyclins

Proteins that regulate the timing of the cell cycle in eukaryotic cells.

Cancer

A disorder in which some of the body's own cells lose the ability to control growth.

Asexual Reproduction

Reproduction involving a single parent that results in offspring that are genetically identical to the parent.

Binary Fission

A single cell duplicates its genetic material and divides into two equal daughter cells, common in prokaryotes like bacteria.

Budding

An outgrowth of cells from a parent organism capable of producing an entirely new, genetically identical organism.

Vegetative Reproduction

Production of genetically identical plants from horizontal stems, plantlets, or roots.

Sporulation

Asexual reproduction by the production and release of spores, common in fungi.

Regeneration

The process by which new cells replace cells that have died or been removed.

Auxins

Hormones that promote stem and root growth and regulate tropisms.

Ethylene

A gas hormone that ripens fruit and causes leaves to drop.

Cytokinins

Hormones that stimulate cell division.

Ecology

The scientific study of interactions between organisms and their environment.

Biotic Factors

The living components of an ecosystem, such as plants, animals, fungi, and bacteria.

Abiotic Factors

The nonliving components of an ecosystem, including temperature, water, sunlight, soil, and $pH$.

Organism

A single living individual of a species.

Population

All individuals of the same species living in a particular area at a given time.

Community

All populations of different species living and interacting in the same area.

Ecosystem

A community of organisms along with the abiotic (nonliving) factors in their environment.

Biome

A large geographic region characterized by its climate and the dominant types of organisms found there.

Biosphere

The global sum of all ecosystems on Earth; every place where life exists.

Autotroph (Producer)

An organism that produces its own food from inorganic molecules, typically through photosynthesis or chemosynthesis.

Heterotroph (Consumer)

An organism that cannot make its own food and must consume other organisms for energy.

Photosynthesis

The process by which plants, algae, and some bacteria convert sunlight, $CO_2$, and water into glucose and oxygen.

Chemosynthesis

The process by which certain bacteria use chemical energy (such as hydrogen sulfide) instead of sunlight to produce food.

Primary Consumer (Herbivore)

An organism that feeds directly on producers; the first consumer in a food chain.

Secondary Consumer

An organism (carnivore or omnivore) that feeds on primary consumers.

Tertiary Consumer (Top Predator)

An organism that feeds on secondary consumers and typically occupies the highest trophic level.

Decomposer

An organism (such as bacteria, fungi, or earthworms) that breaks down dead organisms and waste, returning nutrients to the soil.

Food Chain

A linear model showing a single pathway of energy transfer from one organism to the next in an ecosystem.

Food Web

A model showing all the interconnected feeding relationships among organisms in an ecosystem.

Trophic Level

A step in a food chain or food web, defined by how an organism obtains its energy (e.g., producer, primary consumer).

10% Rule

The principle that only about $10\%$ of the energy at one trophic level is transferred to the next; the rest is lost as heat through cellular respiration.

Energy Pyramid

A diagram showing the amount of energy available at each trophic level; always upright because energy is lost at each step.

Biomass Pyramid

A diagram showing the total mass of living organisms at each trophic level in an ecosystem.

Biomass

The total mass of organisms in a given area or at a given trophic level.

Cellular Respiration

The chemical process by which organisms break down food molecules and oxygen, releasing energy and $CO_2$ as a byproduct.

Biogeochemical Cycle

The pathways through which chemical elements and compounds (such as carbon, nitrogen, and water) move between living organisms and the physical environment.

Water Cycle (Hydrologic Cycle)

The continuous movement of water through evaporation, transpiration, condensation, precipitation, runoff, and infiltration.

Evaporation

The process by which liquid water changes to water vapor, entering the atmosphere from bodies of water.

Transpiration

The release of water vapor from plant leaves into the atmosphere.

Condensation

The process by which water vapor cools and changes back into liquid water droplets, forming clouds.

Precipitation

Water falling from clouds to the Earth's surface as rain, snow, sleet, or hail.

Runoff

Water that flows over the land surface into streams, rivers, and eventually oceans, rather than soaking into the ground.

Infiltration

The process by which water seeps into the ground, replenishing groundwater and aquifers.

Carbon Cycle

The movement of carbon atoms through the biosphere, atmosphere, hydrosphere, and geosphere via processes like photosynthesis, respiration, decomposition, and combustion.

Combustion

The burning of organic material (including fossil fuels), which releases stored carbon into the atmosphere as $CO_2$.

Decomposition

The breakdown of dead organisms and organic waste by decomposers, releasing nutrients and $CO_2$ back into the environment.

Nitrogen Cycle

The biogeochemical cycle by which nitrogen is converted between its various chemical forms as it circulates through the atmosphere, soil, water, and living organisms.

Nitrogen Fixation

The process by which certain bacteria convert atmospheric nitrogen gas ($N_2$) into ammonia ($NH_3$), a form usable by plants.

Nitrification

The bacterial conversion of ammonia into nitrites and then nitrates ($NO_3^-$), which plants can absorb from the soil.

Denitrification

The bacterial conversion of nitrates back into nitrogen gas ($N_2$), returning it to the atmosphere.

Assimilation

The process by which plants absorb nitrates from the soil and animals obtain nitrogen by eating plants or other organisms.

Atmosphere

The layer of gases surrounding Earth; contains carbon primarily as $CO_2$ and methane ($CH_4$).

Hydrosphere

All of Earth's water, including oceans, freshwater systems, and water vapor; stores dissolved carbon and calcium carbonate.

Geosphere

The solid Earth, including rocks, minerals, and soil; stores carbon in fossil fuels, limestone, and sediments.

Competition

An interaction in which two or more organisms vie for the same limited resource, such as food, water, or space.

Intraspecific Competition

Competition between members of the same species for a shared resource.

Interspecific Competition

Competition between members of different species for a shared resource.

Predation

An interaction in which one organism (the predator) hunts and kills another organism (the prey) for food.

Herbivory

An interaction in which an animal feeds on a plant.

Symbiosis

A close, long-term interaction between two species living in direct contact.

Mutualism

A symbiotic relationship in which both species benefit from the interaction (e.g., bees pollinating flowers while collecting nectar).

Commensalism

A symbiotic relationship in which one species benefits and the other is neither helped nor harmed (e.g., barnacles on a whale).

Parasitism

A symbiotic relationship in which one species (the parasite) benefits at the expense of the other (the host), causing it harm.

Predator-Prey Dynamics

The cyclical relationship between predator and prey populations, where changes in one population directly affect the other.

Keystone Species

A species that has a disproportionately large effect on its ecosystem relative to its abundance; its removal causes dramatic changes in the food web.

Trophic Cascade

A series of changes across multiple trophic levels in a food web, triggered by the addition or removal of a top predator or keystone species.

Group Behavior

Behaviors performed by animals in groups (such as flocking, herding, schooling, or pack hunting) that increase survival and reproduction.

Population Growth Rate

The change in population size over time, calculated as $(births + immigration) - (deaths + emigration)$.

Exponential Growth (J-curve)

A pattern of population growth in which the population size increases at an accelerating rate due to unlimited resources and few limiting factors.

Logistic Growth (S-curve)

A pattern of population growth in which rapid initial growth slows and levels off as the population approaches carrying capacity.

Carrying Capacity (K)

The maximum number of individuals of a species that an environment can sustainably support, given the available resources.

Limiting Factor

Any factor that restricts the growth, abundance, or distribution of a population in an ecosystem.

Density-Dependent Factor

A limiting factor whose effect on a population increases as population density increases (e.g., competition, disease, predation).