Levels of Organisation

Different levels of complexity in which living matter is structured.

Atomic & mollecular level

• All matter is made up of very small elements called atoms

• Atoms come together to form molecules, which are held together by chemical bonds

• Atoms in living matter are called bioelements, which then form biomolecules

• The main bioelements in a human being is known as CHON - carbon, hydrogen, oxygen and nitrogen

Organism level

• A tissue is a group of cells which all perform the same function

• Tissues are grouped into organs

• Organs joing together to form organ systems

• Organ systems form a multicellular organism: the human being

Cells & Organelles

Eukaryotic cells

• Plasma membrane is a thin layer that protects the cell and regulates exchanges of substances

• The nucleus is a large spherical structure that contains genetic material which organises the cell’s activity

• Cytoplasm is formed from a thick aqueous liquid called cyostol that contains different substances and cell organelles. It’s where chemical reactions take place

• The nuclear membrane contains nuclear pores that allows substances to be exchanged between the nucleus and the cytoplasm

• The nucleoplasm is made up of a thick aqueous liquid which contains DNA

• Chromatin is the network of all DNA fibres and proteins, which then become chromosomes when the cell divides

• The nucleolus is a spherical structure inside the nucleus where the components of ribosomes are made

Cell differentation

• All cells that make up the human body originates from a single celled called zygote

• The cells later become specialised to perform specific tasks

• Differentiation is the process in which the shape and structure of a cell changes in order to perform a specific function

Tissues

A tissue is a group of cells that are specialised to perform the same function

Epithelial tissue

• It’s made up of layers of cells packed together so closely that there is no space between them

Types:

• Covering epithelium covers and protects outside surfaces and internal cavities - mucus membranes

• Glandular epithelium forms glands which are responsible for secreting substances - sweat glands

Connective tissue

• Connective tissue is made up of cells separated by fibres an intercellular substance called matrix

Types:

• Reticular connective tissue has an extensive gel-like matrix that contains abundant fibres, it fills in organs and the spaces between them and forms tendons

• Adipose tissue has a matrix with low levels of intercellular substance, its cells store fat as an energy reserve and for thermal insulation, as its found under the skin

• Cartilaginous tissue has a solid and elastic matrix, and covers the joints to prevent deterioration

• Osseous (bone) tissue has solid and hard matrix, since there are calcium salts present. This tissue forms bones

• Blood has a liquid matrix called plasma which has blood cells suspended in it

Muscle tissue

• Muscle tissue is made up of elongated cells that group together to form muscle fibres that are able to contract and relax. It’s the tissue responsible for body movement

Types:

• Skeletal striated muscle tissue forms the muscles of the locomotor system and can be moved voluntarily

• Cardiac striated muscle tissue forms the walls of the heart. It contracts involuntarily

• Smooth muscle tissue is found in the walls of various organs like the stomach and bladder. It contracts involuntarily

Nervous tissue

• Nervous tissue is made up of two types of cells:

  1. Neurons, which perceive & react to stimuli & control the body’s activity

  2. Glial cells, which are found amongst neurons and protect & supply them with nutrients

Organs and systems

Systems involved in nutritional functions:

• Digestive: transforms food into nutrients, which are then absorbed into the bloodstream

• Respiratory: exchanges oxygen and carbon dioxide

• Circulatory: uses blood to transport substances throughout the body

• Lymphatic: works together with the circulatory system to transport substances

• Excretory: takes waste substances from the blood and eliminates them from the body

Systems involved in the interaction function:

• Nervous: receives information from the outside environment and generate signals, which then uses to coordinate the body

• Endocrine: works with the nervous system as it generates signals that induce responses in certain organs

• Muscular and skeletal: they make up the locomotor system that’s controlled by the nervous system and generate movement

Systems involved in the reproduction function

• Female reproductive: produces female gametes and nurtures and protects the embryo during its development

• Male reproductive: produces male gametes

Homeostasis: all the physiological processes that keep the internal environment stable

Microscope