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Explain the hierarchical structural organisation of organelles, cells, tissues, organs, systems, and organisms

Organelles -> cells -> tissues -> organs -> systems -> organisms
Specialised cells make up tissues with different types of tissues forming organs that carry out particular function within an organ.


Explain characteristics of unicellular organisms

• Contain only one cell responsible for all life processes
• Simple structure
• Limits metabolic reactions
• Large surface area for all substances to diffuse across
• All prokaryotes are unicellular


Example of a unicellular organism

Bacteria (salmonella)


Explain characteristics of colonial organisms

• Cells that form a cooperative group (colony) but can survive on their own
• Could be classed as a single celled organism
• More efficient as a colony


Example of a colonial organism

EXAMPLE: Blue-bottle


Explain characteristics of multicellular organisms

• Made up of different types of cells
• Similar cells grouped together that communicate to perform specialised functions that combine together for efficient functioning
• Rely less on diffusion and are less efficient
• All cells have the same DNA
• Could not survive by themselves


Example of a multicellular organism

Animals and Plants


Where do specialists cells come from?

All specialised cells originate from cells that are known as stem cells. These stem cells are undifferentiated and are able to divide many times of a long period and become specialised. Once cells have become specialised to form a particular type of cell, they lose their capacity to develop into other types of cells.


What is a part in the body that exchanges substances with the environment and has structural features that allow them to increase their surface area to volume ration ultimately allowing them to exchange the required materials more efficiently

the alveoli


explain the role of the respiratory system

• Work with the cardiovascular system
• Transports oxygen to every cell and remove carbon dioxide.
• Needs air which must be taken in from the environment
• Oxygen in atmosphere transferred into the blood
• Different animals use the respiratory system differently
• Gills, tracheal system – insects


structures in the respiratory system- the pharynx?

Connects the nasal cavity & mouth to the larynx. It is a pathway for both food and air.


structures in the respiratory system- the larynx?

Responsible for ensuring food & air go into the proper channels.


structures in the respiratory system- the epiglottis?

A flap of cartilage which prevents food entering.


structures in the respiratory system- the trachea?

Called windpipe. Is very flexible & mobile.
It contains cells which remove foreign particles from the air.
Divides into two bronchi


structures in the respiratory system- the bronchi?

There are two bronchi leading to each lung.
The bronchi further divide into bronchioles.


structures in the respiratory system- the bronchioles?

To ensure that incoming air is supplied to each alveolus.


structures in the respiratory system- the lungs?

Enclose the structures of the body responsible for gas exchange Bronchioles & alveoli.
The lungs are mainly air spaces where internal gas exchange occurs.


structures in the respiratory system- the alveoli?

Alveoli are small air-filled sacs.
- Increased SA
- Thin moist membrane
- Near blood supply (capillaries


structures in the respiratory system- the capillaries?

Gas exchange occurs through diffusion (concentration gradient).


What happens when stomates are open?

gases are able to diffuse through them


what are lenticels?

• Gas exchange pores
• Found in the woody parts of the plant e.g. trunk and branches
• Composed of clusters of loose cells in the bark layer
• Diffusion of oxygen, carbon dioxide and water vapour is relatively slow


what are pneumatophores?

gas exchange aerial roots, found in mangroves because they live in muddy soil.


explain the structure of the stomata

• Tiny pores that cover epidermis
• Gas enters and leaves
• Each has a pair of guard cells
- Open and close throughout day
- Have chloroplast
- Reduce water loss
• Stomata in grooves
- as leaf dehydrates grooves close - reduced water loss
• Stomata at bottom of pits - reduced water loss
• Sunken of stomata - reduced water loss


Do unicellular organisms rely on diffusion?

Due to their large surface area diffusion is very efficient and have no need for transport systems.


What are heterotrophs

Organisms that feed on others because they cannot provide their own energy supply


What are autotrophs

Organisms that can make their own energy and do not depend on others.


Explain the steps of obtaining nutrients and energy from food

1. Ingestion – intake of food (eating)
2. Digestion – breakdown of food into soluble molecules that can be easily absorbed
3. Absorption – basic units of food absorbed into the bloodstream
4. Assimilation – turning the ‘food’ into tissue
5. Egestion – elimination of wastes


what is mechanical breakdown (digestion)

Chewing, churning, moving (in mouth)


what is chemical breakdown (digestion)

Break down large complex molecules into simpler molecules with the help of enzymes i.e. lipase, amylase in salvia


explain the structure of the small intestine

long with a large surface area (good for absorption). It has an internal surface compromised of millions of tiny folds called villi.


explain the function of the small intestine

- absorbs nutrients and minerals from food like glucose, water and salts. Enzymes produced in the pancreas, small intestine, and bile from the liver and gall bladder break down food products to facilitate nutrient and water absorption.


explain the structure of the xylem

Xylem vessels are long, narrow, hollow tubes containing no living material and impregnated with bands or spirals of lignin. They are joined end to end and provide a continuous pathway from the roots through the stem and to the leaves for water transport.


what does lignin do?

provides strength to stop the vessels from collapsing.


what does the tracheids do?

transport water and are elongated with end walls that taper to a point and also impregnated with lignin


what is transpiration

Loss of water from plants by evaporation of water vapour through the stoma of plant leaves.


explain diffusion

the movement of a substance from a region where it has a high concentration to a region where it has a low concentration


aerobic respiration word equation

Glucose + oxygen = water + carbon dioxide + (energy) ATP


aerobic meaning

using oxygen


photosynthesis word equation

carbon dioxide + water ---> (sunlight chlorophyll) ---> glucose + oxygen


role of photosynthesis in ecosystems

The form of glucose enables the conversion of radiant energy into chemical energy to provide a form of energy to sustain life in the food chain