1 The nature and variety of living organisms - iGCSE Biology Edexcel good one

1.1 understand how 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.

• Move

• Respire

• Sensitivity (respond to their surroundings)

• Homestasis (control their internal conditions)

• Grow and develop

• Reproduce move

• Excrete their waste

• Nutrition

(MRS H GREN)

1.2 describe the common features shown by eukaryotic organisms: plants, animals, fungi and protoctists

PLANTS

Eg: herbaceous legumes (peas), cereals (wheat)

Multicellular

Cells contain a nucleus, chloroplasts and cellulose cell walls

All feed by photosynthesis

Store carbohydrates as starch or sucrose

Contain a large, central cell vacuole

ANIMALS

Eg: humans (mammals), butterflies (insects)

Multicellular

Cells contain a nucleus but no cell walls or chloroplasts

Feed on organic substances made by other living things

Store carbohydrates as glycogen

FUNGI

E.g. moulds, mushrooms, yeast

Most are multicellular with a mycelium of thread-like structures called hyphae which have many nuclei but some are single-celled (eg yeast is single celled)

Cells have nuclei and cell walls made from chitin

Feed by saprotrophic (on dead or decaying material) or parasitic (on live material) nutrition by secreting extracellular enzymes onto the food

May store carbohydrates as glycogen

PROTOCTISTS

E.g. Amoeba (like an animal), Chlorella (like a plant)

Most are unicellular

All have a nucleus; some may have cell walls and chloroplasts, meaning some protoctists photosynthesize like plants and some feed on organic substances made by other living things like animals

1.3 describe the common features shown by prokaryotic organisms such as bacteria

Prokaryotes do not have a membrane-bound nucleus or membrane-bound organelles inside their cells.

Unicellular and microscopic.

Have a cell wall, cell membrane, cytoplasm and plasmids.

Some can carry out photosynthesis but they mainly feed off other organisms, either dead or alive.

1.4 understand the term pathogen and know that pathogens may include fungi, bacteria, protoctists or viruses

An organism that causes disease

Fungi, protoctists, bacteria and viruses can all be pathogens

VIRUSES

E.g. Influenza virus

Much smaller than bacteria

do not carry out all the life processes, not living

Parasitic - reproduce inside host cells by hijacking the cell's mechanisms to make multiple copies and then bursts out of the cell to spread throughout the host

Able to infect every type of living cell

The envelope is used to gain entry into host cells

The capsid is a protein coat used to protect the genetic information

The DNA or RNA contains the code for building new viruses