Biology Definitions Review

These flashcards cover key definitions in biology, helping to prepare for the exam.

Active Transport

The movement of molecules and ions in and out of the cell through the cell membrane against a concentration gradient, using energy from respiration.

Movement

An action by an organism or part of an organism causing a change of position or place.

Sensitivity

The ability to detect stimuli in the internal or external environment and to make responses.

Growth

A permanent increase in size and dry mass by an increase in cell number, cell size, or both.

Excretion

The removal of waste products of metabolism, toxic materials, and substances in excess of requirements from organisms.

Species

A group of organisms that can reproduce to produce fertile offspring.

Binomial Nomenclature

An internationally agreed system in which the scientific name of an organism is made up of two parts: the genus and species.

Diffusion

The net movement of molecules and ions from a region of higher concentration to a region of lower concentration down a concentration gradient, due to random movement.

Osmosis

The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.

Enzymes

Protein molecules that act as biological catalysts.

Catalyst

A substance that increases the rate of chemical reactions without being used up or changed.

Photosynthesis

The process by which plants make carbohydrates from simple raw materials using energy from light.

Nutrition

A daily intake of seven nutrients—carbohydrates, proteins, lipids, vitamins, minerals, water, and fiber—in the correct amounts to provide energy and raw materials for healthy growth and tissue repair.

Ingestion

The taking in of substances into the body through the mouth.

Digestion

The breakdown of large, insoluble molecules into small, soluble molecules by mechanical and chemical processes.

Absorption

The movement of small, soluble food molecules and ions through the wall of the intestine into the blood.

Assimilation

The movement of digested food molecules into the cells of the body, where they are used and become part of the cells.

Egestion

The passing out of food that has not been digested or absorbed.

Transpiration

The loss of water vapor from plant leaves by evaporation of water at the surfaces of the mesophyll cells, followed by the loss of water vapor through stomata.

Translocation

The movement of sucrose and amino acids in the phloem from the regions of production (source) to regions of storage or utilization in respiration or growth.

Pathogen

A microorganism that causes disease.

Communicable Disease

A disease caused by a pathogen that can be passed from one host to another.

Antigens

Chemicals found on the surface of pathogens that are recognized by the body as foreign.

Immune Response

Defense against a pathogen by antibody production in the body.

Passive Immunity

A short-term defense against a pathogen by antibodies acquired from another individual.

Respiration

Chemical reactions inside cells that break down nutrient molecules and release energy.

Aerobic Respiration

Chemical reactions inside cells that use oxygen to break down nutrient molecules and release a large amount of energy.

Deamination

The removal of the nitrogen-containing part of amino acids to form urea.

Synapse

A junction between two neurons.

Reflex Action

Automatic, rapid, integrating, and coordinating responses to stimuli.

Receptors

Groups of receptor cells that respond to specific stimuli (e.g., light, sound, chemicals).

Hormones

A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.

Gravitropism

A response in which parts of a plant grow towards or away from gravity.

Phototropism

A response in which parts of a plant grow towards or away from the direction of light.

Homeostasis

The maintenance of a constant internal environment.

Drugs

Any substance taken into the body that modifies or affects the chemical reactions in the body.

Antibiotics

Substances that kill bacteria but do not harm other living cells, mostly made by fungi.

Reproduction

The process that produces more organisms of the same kind; it can be sexual or asexual.

Asexual Reproduction

A process resulting in the production of genetically identical offspring from one parent.

Sexual Reproduction

A process involving the fusion of the nuclei of two gametes to form a zygote, producing offspring that are genetically different.

Gametes

Sex cells produced by meiosis (reduction division), reducing the chromosome number to half, so that when gametes fuse, the zygote regains the full number of chromosomes.

Pollination

The transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower on the same plant.

Cross-Pollination

The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species.

Fertilization

The fusion of nuclei of sperm and egg, forming a diploid nucleus and creating a zygote.

Implantation

The sinking of the embryo into the spongy lining of the uterus.

STIs

Infections that can be transmitted via body fluids during sexual intercourse, caused by bacteria or viruses.

Inheritance

The transmission of genetic information from generation to generation.

Chromosome

A thread-like structure of DNA carrying genetic information in the form of genes.

Homologous Chromosomes

A pair of chromosomes with the same structure, carrying genes for the same characteristics in the same position, one from the mother and one from the father.

Gene

A length of DNA that codes for one protein.

Alleles

A version of a gene or any of two or more alternative forms of a gene.

Haploid

A nucleus containing a single set of unpaired chromosomes.

Diploid

A nucleus containing two sets of chromosomes.

Mitosis

A nuclear division that gives rise to two genetically identical cells.

Stem Cells

Un-specialized cells that divide by mitosis to produce daughter cells that can become specialized for specific functions.

Meiosis

A nuclear division in which the chromosome number is halved from diploid to haploid, resulting in the formation of four genetically different cells.

Genotype

The genetic makeup of an organism.

Phenotype

The observable features of an organism.

Homozygous

An individual having two identical alleles for a particular gene.

Heterozygous

An individual having two different alleles for a particular gene.

Dominant Allele

An allele that is always expressed if it is present (represented by a capital letter, e.g., B).

Recessive Allele

An allele that is only expressed when there is no dominant allele present (represented by a lowercase letter, e.g., b).

Pedigree

A diagram showing the inheritance of a given characteristic within a family, used to predict cross-breeding results.

Sex-Linked Characteristics

A characteristic in which the gene responsible is located on a sex chromosome.

Variation

Differences between individuals of the same species.

Mutation

A sudden, unpredictable change in the base sequence of DNA.

Adaptation

An inherited functional feature of an organism that increases its fitness.

Survival Rate

The probability of an organism surviving and reproducing in its environment.

Evolution

Changes in the adaptive features of a population over time as a result of natural selection.

Natural Selection

A process resulting from natural selection by which populations become more suited to their environment over many generations.

Population

A group of organisms of one species living in the same area at the same time.

Community

All of the populations of different species in an ecosystem.

Habitat

A place where an organism lives.

Ecosystem

A unit containing the community of organisms and their environment, interacting together.

Food Chain

A diagram showing the flow of energy from one organism to the next, starting with a producer.

Food Web

A network of interconnected food chains.

Ecological Niche

The position of an organism in a food chain, food web, or pyramid of biomass or numbers.

Autotroph

An organism that makes its own organic nutrients, usually using energy from sunlight through photosynthesis.

Heterotroph

An organism that gets energy by feeding on other organisms.

Herbivore

An animal that eats plants.

Carnivore

An animal that eats another animal.

Detritivore

An organism that gets its energy from dead matter or waste organic materials; they are extremely important because they help recycle substances.

Biotechnology

The use of living organisms (usually microorganisms) to make substances that we want.

Genetic Engineering

The process of changing the genetic material of an organism by removing, changing, or inserting individual genes.

Eutrophication

The reduction in oxygen levels in water, leading to the death of all aquatic life that respires aerobically.

Sustainable Resource

A resource that is produced as rapidly as it is removed from the environment, ensuring it does not run out.

Sustainable Development

Development that meets the needs of an increasing human population without harming the environment.