The Nature and Variety of Living Organisms (Section 1)

Characteristics of Living Organisms (Section 1a)

1.1 Understand that living organisms share the following characteristics: 

• they require nutrition 
• they respire 
• they excrete their waste 
• they respond to their surroundings 
• they move 
• they control their internal conditions 
• they reproduce 
• they grow and develop. 

All living organisms share the same eight basic characteristics. They must have all of these characteristics in order to count as being a living organism, and to therefore count as being alive. 

• They require nutrition. 

All living organisms need nutrients to provide them with energy for growth and tissue repair. These nutrients required from food include; fats, protein, vitamins, minerals and carbohydrates.

• They respire 

The process in which organisms release energy from their food.Nutrient molecules are broken down in chemical reactions, releasing energy.

• They excrete their waste 

Removal of toxic materials from the body. Waste products like carbon dioxide have to be removed from the body and this is done through a process known as excretion. 

• They respond to their surroundings 

Living organisms react to changes in their surroundings. An example of this is the way in which plants can grow towards a light source if light is scarce in the environment. 

• They move 

Living organisms move towards and away from things. 

• They can control their internal conditions (homeostasis)

This is the ability to control their internal conditions, such as temperature and water content, and keep this at the level needed in order for them to survive and function. 

• They reproduce 

Living organisms produce offspring and this allows for their species to survive. 

• They grow and develop

Living organisms grow and develop until they reach their adult form. 

The best way to remember these characteristics is through the acronym: Mrs Gren. 

Movement 

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

The only characteristic not included in this acronym is homeostasis, the ability to control internal conditions. 

b) Variety of living organisms 

1.2 describe the common features shared by organisms within the following 
main groups: plants, animals, fungi, bacteria, protoctists and viruses, and 
for each group describe examples and their features as follows (details of life 

cycle and economic importance are not required)

Plants;

• Multicellular
• They have chloroplasts (can photosynthesise) 
• Their cells have cell walls (made of cellulose)
• Store carbohydrates as sucrose or starch. 
• Examples include; flowering plants like cereals (maize) and herbaceous legumes (peas and beans)

Maize.

Animals; 

• Multicellular
• Don't have chloroplasts (cannot photosynthesise)
• Their cells do not have cell walls.
• Most have nervous coordination. Can respond rapidly to changes in their environment. 
• They can usually move around from one place to another.
• Often store carbohydrates in the form of glycogen. 
• Examples; mammals and insects.

                                                       Typical housefly.

Fungi;

• Some are single-celled
• Others have body called mycelium (made up of thread like structures,) contain lots of nuclei. 
• They cannot photosynthesise.
• Their cell walls have cell walls (made of chitin.)
• Most are saprotrophic feeders.
• Can store carbohydrates as glycogen. 
• Examples; years and mucor.

Different examples of fungi. 

Protoctists; 

• Single-celled
• Microscopic
• Some have chloroplasts, similar to plant cells. 
• Others are closer to animal cells. 
• Examples: chlorella (plant-cell like) and amoeba (animal-cell like, lives in pond water.)

Chlorella

Bacteria:

• Also single-celled and microscopic.
• Do not have a nucleus.
• Have a circular chromosome of DNA.
• Only some can photosynthesise. 
• Most bacteria feed off other organisms, both living and dead. 
• Examples: Pneumoccoccus and Lactobacillus bulgaricus.

Diagram of cross-section of typical bacterium.

Viruses: 

• These are particles, not cells. 
• Smaller than bacteria. 
• Can only reproduce inside living cells.
• Organisms that rely on other organisms in order to survive = parasites. 
• They infect all types of living organisms. 
• Come in varying different shapes and sizes. 
• Have no cellular structure, have protein coat around genetic material. 
• Examples: HIV, influenza virus, tobacco mosaic virus. (Stops tobacco leaves from producing chloroplasts, discolours them.)

                                     Diagram of cross-section of typical flu virus. 

1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria,

protoctists or viruses.

Pathogens are organisms that cause disease.They come in many different forms, including some; fungi, protoctists, bacteria and viruses. For example, plasmodium is a protoctist that causes malaria and influenza virus is a virus that causes flu and HIV.