2.3 living processes in multicellular organisms (p1)

multicellular organisms are….

• made up of more than one cell

• large complex organisms

specialised cells

• multicellular organisms need cell specialisation to enable them to perform different specific functions

• in cell specialisation, cells differentiate to change their shape and structure to become specialised cells to carry out its specific functions

• each specialised cell has structures that are specially adapted to carry out its specific structures

epithelial cell

• flat and thin cells

• coats the surface of organs such as the digestive tract

muscle cell

• arranged as multinuclear striated fibres

• contracts and relaxes to generate movement

nerve cell

• long and thin in shape

• functions in sending nerve impulses

red blood cell

• does not contain a nucleus

• shaped as a biconcave disc

• functions to optimise transportation of oxygen

white blood cell

• can change shape

• functions in destroying pathogens

sperm cell

• has a long tail to enable it to swim towards the ovum in the fallopian tube

• the head carries a set of chromosomes from the male

spongy mesophyll cell

• oval in shape, has chloroplasts

• cells are loosely arranged on lower surface of leaf with lots of air space in between

• large air space facilitates diffusion of gases from the inside of the leaves to the palisade mesophyll cells

palisade mesophyll cell

• rectangular in shape, has high chlorophyll density

• consists of long cylindrical cells, arranged vertically and close to each other on upper surface of leaf

• allows maximum absorption of energy of sunlight for photosynthesis

xylem vessel

• long, continuous hollow fine tube from the root to all the other parts of the plant

• functions in transporting water and mineral salts from the roots to the other parts of the plants

sieve tube element

• long cylindrical tubes arranged from end to end

• transports organic materials from leaves to storage organs such as fruits

root hair cell

• has a long fine projection which adds surface area for the absorption of water and mineral salts from the soil

guard cell

• modified lower epidermal cells with the thicker cell wall on the inner side

• controls the opening and closing of the stoma. stoma is the opening that allows the exchange of oxygen and carbon dioxide

cell organisation is….

arrangement and organisation of specialised cells into different levels to form a complex multicellular organism

cell ➡ tissue ➡ organ ➡ organ system ➡ multicellular organism

tissues are…

a group of cells that have the same structure and function and are arranged together to carry out a specific function

four main types of tissue: epithelial tissue, muscle tissue, nerve tissue and connective tissue

epithelial tissue : structure

• consists of epithelial cells arranged in one continuous layer which is one cell thick

• covers the outer surface (skin) and hollow surfaces in the body (e.g. the digestive tract + respiratory tract)

epithelial tissue : functions

• protects the underlying cells from mechanical injury

• acts to absorb food and water via diffusion

• forms secretory glands which produce secretions

epithelial tissue : types

epithelial tissue lines the…

• esophageal wall

• respiratory tract, alveolus of the lungs + blood vessels

• tubules, glands and kidney ducts

• the small intestinal wall

muscle tissue : types

muscle tissue is made up of muscle cells that can contract and relax to produce movement

• smooth muscle (digestive tract, urinary tract, blood vessel and reproductive tract)

• skeletal muscle (legs and hands)

• cardiac muscle (heart wall)

smooth muscle tissues …

contracts and relaxes to enable involuntary activities such as peristalsis along the digestive tract

skeletal muscle tissues …

contracts and relaxes to enable voluntary movement to generate movement in bones and limbs

cardiac muscle tissues …

builds walls of the heart that contracts to pump blood to the whole body

• cardiac muscle contraction is involuntary

nerve tissue : structure

• made of neuron or nerve cells

• each neuron consists of a cell body and nerve fibre called dendrite and axon

nerve tissue : functions

• detects stimuli and then sends information in the form of an electrical signal (nerve impulses) to the muscles or glands

• regulates and coordinates body activity

connective tissue : structure + function

consists of various types of cells in a matrix of fibre and collagen

• fibrous connective tissue, loose connective tissue, cartilage, blood tissue, bone and adipose tissue

join body structures together, protect, hold and support cells in the body as well as store and transport materials

fibrous connective tissue

form tendons and ligaments. tendons connect bones and muscles, tendons connect bones to bones.

loose connective tissue

under the skin to fix organs in their positions and attach epithelial tissue to other underlying tissues

cartilage

encloses bone tips to absorb shock and prevent the bone from wearing out

blood tissue

in the blood vessels for transportation of nutrients, gases and for body defence and blood clotting processes.

bone

forms the body frame and protects the internal organs

adipose tissue

connective tissues that keep fat below the skin dermis and surface of all main organs to store energy and act as an insulator

types of plant tissues…

epidermal tissue, meristem tissue, vascular tissue, ground tissue

epidermal tissue

• consists of one layer of epidermal cells

• covers the surface of plant to form the epidermis of leaves stem, root

• protects underlying tissues, protects against water loss

meristem tissue

consists of meristem cells that always divide by mitosis to produce new cells for growth

1. apical meristem tissue (at shoot and root tip)

   • divides to increase the length of the root and shoot

2. lateral meristem tissue (cambion and dicotyledon stem)

   • divides to increase the diameter of the stem

vascular tissue

1. xylem tissue

   • transports water and mineral salts from the roots to all parts of the plants

   • ligneous xylem tissue provides support and mechanical strength to the plant

2. phloem tissue

   • transports organic matters (e.g. sucrose and amino acids) from the leaves to all parts of the plant

ground tissue

1. parenchyma tissue

   • functions to store starch, protein and water

   • carries out photosynthesis

2. collenchyma tissue

   • functions to give support to young, non-woody stems

3. sclerenchyma tissue

   • provides support and mechanical strength to all mature parts of the plant