Biology

How are the bodies of fungi organised? Draw diagram(s)

Their body is usually organised into a mycelium made from thread-like structures called hyphae which contain many nuclei (multinucleate). They can also be single celled.

What characteristics do all living organisms share?

MRS GRENC

they move, they respire, they respond to their surroundings (sensitivity) they grow and develop, they reproduce, they excrete waste, they require nutrition, they control their internal conditions.

Every organism can be divided into two types. What are these two types?

Eukaryotes and prokaryotes.

what are the four types of eukaryotic organisms?

Plants, animals, fungi and protoctists

Fill in the following table:

animals

plants

Multi- or uni-cellular?

Do they have chloroplasts?

Cell wall material?

How do they store carbohydrates

animals

plants

Multi- or uni-cellular?

multicellular

multicellular

Do they have chloroplasts?

No – cannot photosynthesise

Yes – can photosynthesise

Cell wall material?

No cell wall

cellulose

How do they store carbohydrates

glycogen

Starch (think of potatoes) or sucrose (think of sugar cane)

Give an example of a herbaceous legume?

Peas or beans. (herbaceous = soft stem i.e. not woody like a tree. legume is an important type of agricultural plant)

Give an example of a flowering plant?

any cereal e.g. maize. (a “cereal” is a type of grass that is harvested for its seeds for us to eat)

Can fungi photosynthesise? Do fungi have a cell wall, and if so, what is it made of? How do they store carbohydrates?

They can’t photosynthesise. Their cell walls are made of chitin. They may store carbohydrate as glycogen

How do fungi feed?

Saprotrophic nutrition: they feed by secreting extracellular enzymes into their environment and absorb the products

Give two examples of fungi

Mucor (has typical hyphae structure) and yeast which is single celled. (Mucor is a type of mould)

What are protoctists? What are their features? Give 3 examples of protoctists. Give an example of a pathogenic protoctist

Protoctists are a type of eukaryote. Some have features like animal cells and some have chloroplasts and features of plant cells.

Examples: 1) Amoeba (lives in pond water). (you don’t need to know this but useful as a memory aid – there is a type of amoeba that lives in pool water and if inhaled will eat your brain). 2) Chlorella – a type of protoctist that has chloroplasts. 3) Plasmodium – the pathogen that causes malaria

Which organisms are prokaryotic?

Bacteria

What are the cellular features of bacteria?

They have a cell wall, cell membrane, cytoplasm and plasmids (small, circular DNA molecules that exist independently of their main circular loop of DNA). Bacteria do not have a nucleus but have a circular chromosome of DNA.

How do bacteria feed?

Some bacteria can carry out photosynthesis but most feed off other living or dead organisms

Give two examples of bacteria?

Latobaccilus bulgaricus is a rod shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia.

What is a pathogen? What kind of organisms can be pathogens

A pathogen is an organism that causes disease. They can be fungi, bacteria, protoctists or viruses. (Prions - special types of proteins - can also cause diseases but this is outside the scope of igcse biology)

Use the characteristics of living organisms to explain why/why not viruses are living

Describe the structure of viruses

They are small particles, smaller than bacteria; they are parasitic and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA

Give two examples of viruses, one that infects humans and one that infects plants

Tobacco mosaic virus that causes discoloration of tobacco plants by preventing formation of chloroplasts

Influenza virus: causes flu. HIV virus causes AIDS