IGCSE Biology: Key Concepts and Terminology

Movement

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

Respiration

Chemical reactions in cells that break down nutrient molecules and release energy for metabolism

Sensitivity

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

Growth

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

Reproduction

The processes that make more of the same kind of organism

Excretion

Removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials and substances in excess of requirements

Nutrition

Taking in of materials for energy, growth and development (plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water)

Classification

Placing organisms into groups based on the features they share

Characteristic

An observable characteristic of an organism

Binomial System

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

Anatomy

The study of the structure of organisms and their parts

Morphology

The study of the shape of the structures of organisms

Ancestor

The individual that we are descended from

Domain

Largest classification group for living organisms

Genus

Classification group above species; used as the first part of the binomial name

Species

A group of organisms with similar characteristics that can breed and produce fertile offspring

Virus

Genetic material (DNA or RNA) surrounded by a protein coat, only living when inside a host.

Bacteria

Unicellular organisms that have DNA but lack a nucleus and membrane bound organelles. They reproduce by Binary fission and have a cell wall.

Fungi

Unicellular and multicellular organisms with a chitin cell wall which feeds saprotrophically. The body is a mycellium made of hyphae and it reproduced using spores.

Plants

Multicellular organisms with chlorophyll and a cellulose cell wall. They are photosynthetic (autotrophic) and reproduce using spores or seeds.

Animals

Multicellular organisms with no cell wall. They are heterotrophic and generally show locomotion.

Unicellular organism

An organism made up of one cell

Multicellular organism

An organism made up of many cells

Autotropic

Organisms that make their own food by combining inorganic molecules to make organic molecules (photosynthesis)

Heterotrophic

Organisms that feed on other living organisms using digestive enzyme to release the nutrients they need

Saprotrophic

Organisms that feed on dead or waste material by secreting digestive enzymes and absorbing the broken down nutrients

Mitosis

A form of asexual reproduction. The genetic material is replicates and the cell splits into two, each half contains an identical copy of the genetic material

Mycelium

The "body" of a fungus, made of a network of threads each thread is called a hyphae

Hyphae

The fine threads that make up the mycelium of a fungus

Gamete

A reproductive cell or group of cells, produced by some plants, that is capable of developing into an adult organism. Can be produced sexually or asexually

Seed

A fertilised ovule with its own food store which is capable of developing into an adult plant. Produced in sexual reproduction

Asexual

Reproduction that involves only one parent and produces offspring that are genetically identical to the parent (clones)

Sexual

Reproduction that involves the fusion of male and female gametes in fertilization and produces genetically different offspring

Chitin

A fibrous carbohydrate forming the exoskeleton of arthropods and the cell walls of fungi.

Locomotion

The ability to move from one place to another

Ferns

Has vascular tissue (xylem and phloem). Have true root, stem and leaves.

Ferns

Has vascular tissue (xylem and phloem). Have true root, stem and leaves. Has underground root and stem. Has large leaves called fronds. Reproduces using spores.

Angiosperm

Has vascular tissue (xylem and phloem). Have true, root stem and leaves. Have flowers. Produce seeds in a fruit. Use wind or animal pollination.

Monocot

1 cotyledon in seed, parallel veins on leaves, vascular bundles scattered in stem, pith in centre of root, flower parts in 3's, adventitious roots.

Dicot

2 cotyledons in seed, network of veins on leaves, vascular bundles in a ring in the stem, xylem in centre of root, flower parts in 4's or 5's, main tap root with branches.

Endosperm

The food store in the seed which is used by the developing plant.

Invertebrate

An animal without a backbone.

Vertebrate

An animal with a backbone.

Arthropod

A phylum of animals that all have a chitin exoskeleton and jointed paired limbs, and are segmented.

Crustacean

Class of Arthropods: exoskeleton includes a carapace; 5 pairs of legs; gills under carapace; often have pincers (claws); 2 pairs of antennae; cephalothorax and abdomen.

Myriapod

Group of Arthropods: pairs of limbs on each segment; one pair of antennae; head and body.

Arachnid

Class of Arthropod: 4 pairs of legs; more than one pair of eyes; no antennae; cephalothorax and abdomen.

Insect

Class of Arthropod: head, thorax and abdomen; 3 pairs of legs; compound eye; 2 pairs of wing (most); specialised mouth parts, 1 pair of antennae.

Cephalothorax

Head joined with thorax.

Thoracic cavity

Chest cavity.

Chordata

Phylum including the vertebrates.

Fish

Class of Chordata: slimy scales; gills; fins; lateral line; eggs with no shell; live and reproduce in water (external fertilisation and development); ectothermic.

Amphibian

Class of Chordata: moist smooth skin and small lungs for gas exchange; 4 limbs; hind limbs webbed; eggs with jelly-like shells; reproduce in water (external fertilisation and development); ectothermic.

Reptile

Class of Chordata: Dry scaly skin; 4 limbs (except snakes); tail; eggs with leathery shells; reproduce on land (internal fertilisation; external development); ectothermic.

Bird

Class of Chordata: feathers; wings; beak; scales on legs; eggs with hard calcareous shells; reproduce on land (internal fertilization; external development); endothermic.

Mammal

Class of Chordate: fur; pinna (external ear); whiskers; mammary glands producing milk; live young born; reproduce on land (internal fertilisation and development); endothermic.

Ectothermic

Body temperature depends on the temperature of the environment (varies).

Endothermic

Body temperature remains constant; use metabolic energy.

Dichotomous keys

A set of questions based on observable features which are used to identify living organisms

Cell

The basic structural and functional unit of life

Organelle

A structure within a cell

Cell membrane

The partially-permeable barrier that regulates substances entering and leaving a cell

Selective permeability

Allows some substance to pass through

Cytoplasm

The jelly-like material in which all a cell's organelles are found, and in which most cellular processes and reactions occur

Mitochondria

The site of energy release by aerobic respiration

Nucleus

The location of a cell's DNA in chromosomes, controls the cells functions

Vacuole

A fluid filled sac. The fluid is surrounded by a membrane

Endoplasmic reticulum

A system of membranes running through the cytoplasm for transporting substance

Ribosome

The site of protein synthesis

Cell wall

The rigid external coat made of cellulose that protects and supports plant cells

Central vacuole

The fluid-filled cavity found in plant cells that stores water and nutrients

Chlorophyll

The green pigment found in chloroplasts

Chloroplast

The site of photosynthesis in plant cells

Photosynthesis

The chemical reaction in which light energy is used to convert carbon dioxide and water into glucose and oxygen

Adaptation

Adapting structure to perform a job

Specialized cells

Having different specialised cells

Ciliated cells

Has cilia (hairs) which move to push substances over the surface e.g. mucus in the trachea and bronchi

Root hair cells

Has an elongated projection to increase surface area for the absorption of water

Xylem vessels

Elongated, hollow, dead cells with no cell contents or end walls to reduce resistance to flow and allow rapid transport of water; the cell wall contains lignin for waterproofing and support

Lignin

A complex biochemical that adds strength to the cell wall of some plant cells

Palisade cells

Rectangular cells containing many chloroplasts for photosynthesis

Neurons

Highly elongated cells which conduct electrical impulses

Red blood cells

Transports oxygen; biconcave disc to increase surface area for absorption, no nucleus to increase the volume available for the haemoglobin which carries the oxygen

Sperm cell

A male gamete, has half the normal amount of genetic material and a tail to swim

Egg cell

A female gamete, has half the normal amount of genetic material and contains a large quantity of nutrients

Tissue

A group of cells with similar structures working together to perform a shared function

Organ

A structure made up of a group of tissues, working together to perform specific functions

Organ system

A group of organs with related functions, working together to perform body functions

Size of specimens

Size of the image divided by size of the object

Size in meters

1 x 10-3 m (0.001 m); mm

Size in micrometers

1 x 10-6 m (0.000001 m); µm

Diffusion

The net movement of molecules from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement

Concentration gradient

Difference in concentration between 2 areas

Solute

A dissolved substance

Solvent

The liquid a solute dissolves in

Osmosis

The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane

Water potential

A measure of the amount of water in a solution; pure water = 0; solutions are negative.

Lysed cell

A cell which has broken open

Crenated cell

An animal cell that has shrivelled up

Plasmolysis

When so much water is lost from the cell that the cytoplasm no longer fills the cell