Biology Gateway (OCR)

Cell Theory

The theory that states cells are fundamental to life, all living things are made of cells, cells are basic units of life, and all cells come from pre-existing cells.

Nucleus

The command center of a cell containing chromosomes made of DNA that directs cellular activities.

Cytoplasm

The gel-like substance filling the cell that holds organelles and is the site of metabolic reactions.

Cell Membrane

The selectively permeable outer boundary of the cell that controls the movement of substances in and out.

Mitochondria

The power generators of the cell where aerobic respiration occurs, producing ATP from glucose.

Ribosomes

Tiny organelles responsible for protein synthesis, assembling amino acids into proteins.

Cell Wall

A rigid outer layer in plant cells that provides structural support and protection, made mainly of cellulose.

Vacuole

A large fluid-filled sac in plant cells that stores nutrients and helps maintain turgor pressure.

Chloroplasts

Organelles that conduct photosynthesis by using chlorophyll to absorb light energy.

Red Blood Cells

Specialized cells adapted for oxygen transport with a biconcave shape and no nucleus.

Nerve Cells

Specialized cells adapted for rapid signal transmission with long, thin structures and myelin sheaths.

Muscle Cells

Cells adapted for contraction containing protein filaments and many mitochondria.

Root Hair Cells

Cells adapted for absorption of water and minerals with long projections and no chloroplasts.

MRS GREN

An acronym for the fundamental processes of life: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Aerobic Respiration

A metabolic process that fully breaks down glucose using oxygen to produce energy (ATP).

Anaerobic Respiration

A process that partially breaks down glucose without oxygen, resulting in lactic acid in animals or ethanol in yeast.

Photosynthesis

The process by which green plants convert light energy into chemical energy in the form of glucose.

Light-dependent Reactions

The first stage of photosynthesis where light energy is converted to ATP and NADPH, with oxygen released as a byproduct.

Calvin Cycle

The light-independent reactions in photosynthesis where carbon dioxide is converted into glucose.

Diffusion

The passive movement of particles from an area of high concentration to an area of low concentration.

Osmosis

The diffusion of water across a selectively permeable membrane from a region of high water concentration to low.

Active Transport

The movement of substances against a concentration gradient using energy, often involving protein pumps.

Homeostasis

The maintenance of a stable internal environment in the body despite external changes.

Negative Feedback

A control mechanism in homeostasis where a change in a variable triggers a response that opposes the change.

Ecosystem

A community of interacting organisms and their physical environment in a specific area.

Producers

Organisms that make their own food from inorganic substances, typically through photosynthesis.

Consumers

Organisms that cannot make their own food and obtain energy by consuming other organisms.

Decomposers

Organisms that break down dead matter and waste, recycling nutrients back into the ecosystem.

Biodiversity

The variety of life on Earth, encompassing different species, genetic variation, and ecosystems.

Natural Selection

The process where individuals with advantageous traits are more likely to survive and reproduce.

Genotype

The genetic makeup of an individual for a particular trait, represented by alleles.

Phenotype

The observable characteristics of an individual determined by genotype and environmental factors.

Punnett Square

A diagram used to predict the genotypes and phenotypes of offspring from a genetic cross.

Vaccination

The process of introducing weakened or inactive pathogens to stimulate the immune system.

Antibiotics

Medicines that kill bacteria or inhibit their growth, effective against bacterial infections.

Antibiotic Resistance

The ability of bacteria to survive despite the presence of antibiotic medications.

Food Security

The condition where all people have access to sufficient, safe, and nutritious food.

Sustainable Agriculture

Farming practices that meet current food needs without compromising future generations.

Greenhouse Gases

Gases that trap heat in the atmosphere, contributing to global warming and climate change.

Climate Change

Long-term shifts in weather patterns and climate caused mainly by human activities.

Pollution

The introduction of harmful substances into the environment, affecting living organisms.

Deforestation

The clearing of forests for agriculture, urban development, or other land uses.

Ecosystem Services

The benefits that humans derive from ecosystems, like pollination and water purification.

Mutation

A change in the DNA sequence that can lead to genetic variation within a population.

Fossil Record

The history of life on Earth as documented by fossilized remains.

Speciation

The formation of new species due to evolutionary processes, often through reproductive isolation.

Selective Breeding

The human practice of breeding animals and plants for desired traits.

Environmental Factors

Non-living components of an ecosystem, such as temperature, water availability, and light.

Alleles

Different versions of a gene that can result in variation in traits.

Hormones

Chemical messengers produced by glands that regulate various body functions.

Reflex Action

An automatic, rapid response to a stimulus that bypasses conscious control.

Enzyme Activity

The rate at which an enzyme catalyzes a reaction, influenced by temperature and pH.

Transmission of Disease

The mechanisms by which pathogens spread, including direct contact and vectors.

Nutrient Cycling

The process through which nutrients are recycled in ecosystems, enabling productivity.

Global Warming

The increase in Earth's average surface temperature due to rising levels of greenhouse gases.

Genetic Variation

Differences in DNA among individuals, which is crucial for a population's adaptability.

Herd Immunity

Immunity in a population that occurs when a sufficiently high percentage are immune to an infection.

Public Health Surveillance

The ongoing systematic collection and analysis of health data to inform health policies.