Topic 1- Characteristics and classification of living organisms

MRS GREN

A mnemonic that stands for the seven characteristics of living organisms: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Movement

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

Respiration

The chemical reaction in cells that breaks down nutrient molecules and releases 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, cell size, or both.

Reproduction

The processes that create more of the same kind of organism.

Excretion

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

Nutrition

The intake of materials for energy, growth, and development.

Species

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

Binomial System

An internationally agreed system for naming organisms using two parts: genus and species.

Genus

The first part of the scientific name in the binomial system, which is always capitalized.

Species (in binomial naming)

The second part of the scientific name, which is never capitalized.

Kingdom

The largest group in the classification system, under which organisms are grouped based on shared features.

Morphology

The study of the outward appearance of organisms.

Anatomy

The study of the internal structure of organisms.

Dichotomous Key

A tool used by biologists to identify organisms through a series of questions with two alternative answers.

Cytoplasm

The jelly-like substance within a cell that contains all the cell organelles.

Cell Membrane

A semi-permeable barrier that controls what enters and leaves the cell.

DNA

The genetic material present in all living organisms.

Ribosomes

Cell organelles involved in the synthesis of proteins.

Enzymes

Biological catalysts that are involved in metabolic processes, including respiration.

Prokaryote

Single-celled organisms that lack a nucleus, e.g., bacteria.

Protoctists

Predominantly unicellular organisms that may have characteristics similar to plants or animals.

Fungi

Multicellular organisms that do not have chlorophyll and feed through saprophytic or parasitic nutrition.

Plants

Multicellular organisms that contain chloroplasts for photosynthesis and have cell walls made of cellulose.

Animals

Multicellular organisms that do not have cell walls or chloroplasts and can move around.

Arthropods

The largest group of invertebrates, characterized by segmented bodies, limbs with joints, and external skeletons made of chitin.

Invertebrates

Animals that do not have a backbone.

Vertabrates

Animals with a backbone, classified into groups like mammals, birds, reptiles, amphibians, and fish.

Monocotyledons

Flowering plants that have one cotyledon and parallel leaf veins.

Dicotyledons

Flowering plants that have two cotyledons and branching leaf veins.

Viruses

Microorganisms that are not classified as cells, can only reproduce inside living cells, and are often pathogenic.