Section 2 a) Summary

Living organisms are made up of different levels of organisation, each categorised as follows:

Organelle: found within a cell, it helps the cell to carry out different functions, for example mitochondria respires and therefore provide the cell with energy, and a nucleus contains DNA within chromosomes that direct the cell's actions.

Cell: contains organelles, can be an organism on its own (uni-cellular) or part of a larger organism (multi-cellular). Makes up tissues. Can carry out a specific function, e.g. neurones, or nerve cells, transmit electrical impulses around the body, and in plants the palisade cell contains lots of chloroplasts for photosynthesis.

Tissue: made up of similar cells working together to carry out a specific function. Tissues make up organs and carry out vital roles, e.g. muscle tissue allows animals to move as it contracts and relaxes, connective tissues hold organs together and support them in place

Organ: Made up of a group of different tissues, found within organ systems. Carries out one or more specific function, e.g. the skin protects the body and regulates heat, the eyes pick up light that allows us to see

Organ system: a group of organs that work in a system to carry out life processes, e.g. circulatory system pumps blood around the body so oxygen can reach everywhere for respiration, nervous system transmits electrical impulses so the body can react to stimuli

Section 2 a) Key Words

Cell: "Building Block" of life, smallest structural and functional unit of an organism

Organ: A group of tissues working together to carry out 1 or more specific functions

Organelle: A structure within a cell that carries out a function

Organism: An entire living thing, it carries out the seven life processes

Organ System: A group of organs working to carry out specific life functions

Tissue: A group of cells working together to carry out a specific function

Section 2 a) Specification

2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.

Organelles are the specialised structures within a cell that carry out a specific function, e.g. the nucleus, vacuole, etc. They are the smallest level of organisation within an organism.

Cells are made up of organelles and are the smallest unit of life, the "building blocks", if you will, e.g. nerve cells, muscle cells, etc.

Tissues are made up of the lots of the same type of cell working together to carry out a specific function, e.g. palisade mesophyll, nervous tissue, etc.

Organs are groups of tissues working together to carry out a specific function in an organism, e.g. the brain, a leaf, etc.

Organ systems are a group of organs that work together to perform one or more functions, e.g. the nervous system, circulatory system, etc.

Organisms are entire living things that carry out the functions of MRS GREN, e.g. human, cactus