science learning intention 3

Levels of structural organisation in multicellular organisms

The hierarchy from simplest to most complex: organelles $\rightarrow$ cells $\rightarrow$ tissues $\rightarrow$ organs $\rightarrow$ organ systems $\rightarrow$ organism.

Tissue

A group of similar cells working together to perform a shared, specific function.

Organ

A distinct structure composed of different types of tissues working collaboratively to carry out a specific bodily role.

Organ system

A coordinated group of organs functioning together to conduct major life processes in an organism.

Cellular differentiation

The developmental process by which unspecialised cells change and acquire distinct structural features suited to specific functions.

Red blood cell

A specialised animal cell featuring a biconcave disc shape, no nucleus, and haemoglobin to maximise oxygen transport.

Nerve cell (Neuron)

A specialised cell with an elongated axon and branching dendrites designed to conduct electrical impulses rapidly across the body.

Muscle cell

A specialised animal cell packed with mitochondria and contractile protein filaments that shorten and lengthen to produce movement.

Sperm cell

A male reproductive cell equipped with a flagellum, abundant mitochondria for propulsion, and enzymes in the acrosome to penetrate an ovum.

Root hair cell

A plant cell with a long, thin projection that increases surface area to absorb water and dissolved minerals from the soil.

Palisade mesophyll cell

A columnar plant cell situated near the upper surface of leaves and densely packed with chloroplasts to optimise photosynthesis.

Xylem

Hollow, dead plant vessels reinforced with lignin that transport water and dissolved mineral ions upwards from the roots.

Phloem

Living vascular plant tissue with perforated end walls (sieve plates) that translocates dissolved sugars and nutrients throughout the plant.