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Organism

A living thing.

Variation

Differences between individuals of the same species.

Genetic variation

Differences in DNA among individuals.

Discrete variation

Traits with distinct categories (e.g., blood type).

Continuous variation

Traits that vary gradually (e.g., height).

Species (morphological)

Group of organisms with similar structure.

Species (biological)

Group that can breed and produce fertile offspring.

Binomial nomenclature

Two-part naming system (genus + species).

Hybrid

Offspring from two different species.

Geographical isolation

Physical separation preventing reproduction.

Speciation

Formation of a new species.

Chromosome number

Total chromosomes in a typical cell.

Diploid

Cell with two sets of chromosomes.

Karyotype

Display of an organism's chromosomes.

Karyogram

Image of a stained karyotype.

Autosome

Non-sex chromosome.

Sex chromosome

Chromosome that determines sex (X or Y).

Genome

Entire set of DNA in an organism.

Gene

DNA segment coding for a protein.

Allele

Variant form of a gene.

Single-nucleotide polymorphism (SNP)

DNA base difference between individuals.

Genome size

Total DNA amount in a genome.

Gene sequence

Order of DNA bases in a gene.

Sequence (DNA)

Specific order of nucleotides.

Genome sequencing

Determining DNA sequence of the entire genome.

Ethics (in genomics)

Moral issues in genetic research and applications.

Gas exchange

Movement of gases (O₂/CO₂) between organisms and environment.

Diffusion

Movement from high to low concentration.

Surface area-to-volume ratio

Comparison of outer area to internal volume.

Permeability

Ability of a surface to allow substances through.

Moisture

Presence of water aiding gas diffusion.

Concentration gradient

Difference in concentration across a space.

Respiration

Process of releasing energy from food.

Blood flow

Movement of blood through vessels.

Ventilation

Air movement in and out of lungs.

Alveolus (alveoli)

Air sacs in lungs for gas exchange.

Bronchiole

Small airways leading to alveoli.

Surfactant

Substance reducing surface tension in alveoli.

Inspiration

Breathing in.

Expiration

Breathing out.

Diaphragm

Muscle under lungs helping with breathing.

Intercostal muscles

Muscles between ribs aiding breathing.

Abdominal muscles

Help force air out of lungs.

Ventilation rate

Number of breaths per minute.

Tidal volume

Air moved per breath at rest.

Vital capacity

Maximum air exhaled after deep breath.

Inspiratory reserve volume

Extra air inhaled after normal breath.

Expiratory reserve volume

Extra air exhaled after normal breath.

Transpiration

Water loss from plant leaves.

Epidermis

Outer layer of plant or animal cells.

Cuticle

Waxy layer on leaf surface to reduce water loss.

Stoma (stomata)

Pores in leaf for gas exchange.

Guard cell

Cell controlling stomata opening/closing.

Air space

Space in leaf allowing gas movement.

Spongy mesophyll

Loosely packed photosynthetic cells in leaves.

Palisade mesophyll

Densely packed upper leaf cells for photosynthesis.

Vein (in leaves)

Vascular bundle for transport in leaves.

Plan diagram

Simple sketch showing leaf structure layout.

Stomatal density

Number of stomata per leaf area.

Capillary

Small blood vessel for exchange with tissues.

Lumen

Inner space of a vessel.

Wall thickness

Thickness of vessel wall.

Fenestration

Tiny openings in capillary walls for filtration.

Artery

Blood vessel carrying blood away from the heart.

Vein

Blood vessel returning blood to the heart.

Valve

Prevents backflow in veins.

Elastic fibers

Allow vessel walls to stretch and recoil.

Pulse rate

Number of heartbeats per minute.

Heart rate

Frequency of heart contractions.

Skeletal muscles (in circulation)

Help push blood in veins.

Coronary artery

Supplies blood to heart muscle.

Occlusion

Blockage (often in arteries).

Xylem

Vessels transporting water in plants.

Phloem

Vessels transporting food in plants.

Vascular bundle

Group of xylem and phloem in plants.

Cambium

Tissue for new xylem and phloem growth.

Cortex

Plant tissue between epidermis and vascular bundles.

Pith

Central plant tissue in stems.

Epidermis

Outer layer of cells in plant stems/leaves.

Capillary action

Water movement in narrow spaces.

Transpiration pull

Upward water movement from leaf water loss.

Cohesion

Attraction between water molecules.

Dicotyledonous plant

Plant with two seed leaves (cotyledons).

System integration

Cooperation of body systems for function.

Tissue

Group of similar cells performing a function.

Organ

Structure with multiple tissues working together.

Organ system

Group of organs working for a body function.

Emergent property

A new function arising from system components.

Hormonal signaling

Communication using hormones in blood.

Nervous signaling

Fast communication via nerve impulses.

Blood transport

Circulation of substances via blood.

Brain

Central organ of the nervous system.

Spinal cord

Nerve cord connecting brain to body.

Central nervous system (CNS)

Brain and spinal cord.

Sensory receptor

Cell detecting stimuli.

Sensory neuron

Carries signal from receptor to CNS.

Motor neuron

Carries signal from CNS to muscle/gland.

Cerebral hemisphere

Left or right brain half.

Primary motor cortex

Brain area controlling voluntary movement.

Skeletal muscle

Muscle type attached to bones.