The variety of living organisms Edexcel International GCSE Science (Double Award) revision
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In plain words
Living things come in a few very different designs. Plants make their own food. Animals eat. Fungi feed by digesting what they grow on. Protoctists and bacteria are single cells, the bacteria much smaller and simpler. And viruses sit at the edge of life, unable to do anything outside another cell.
Three things to know
- Plants: many cells, chloroplasts, cellulose cell walls, store carbohydrate as starch. Animals: many cells, no cell walls or chloroplasts, nervous coordination, store carbohydrate as glycogen.
- Fungi: a body of thread-like hyphae (a mycelium), cell walls of chitin, no chloroplasts; they feed by releasing enzymes on to dead material and absorbing the products (saprotrophic nutrition). Yeast is a single-celled fungus. Protoctists: single-celled, some like animal cells (Amoeba), some like plant cells (Chlorella).
- Bacteria: single cells with a cell wall but no nucleus, just a loop of DNA and plasmids. Viruses: not cells; a protein coat round DNA or RNA; they reproduce only inside living cells. A pathogen is any organism that causes disease.
Tips and tricks
- Storage carbohydrate: plants store starch, animals and fungi store glycogen.
- Cell walls: plants cellulose, fungi chitin, animals none.
It lands in your notebook with its questions as flashcards.
The variety of living organisms: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What are the cell walls of fungi made of?
Plant cell walls are cellulose; fungal walls are chitin.
How do animals store carbohydrate?
Plants store starch.
What is the body of a fungus made of?
A mass of hyphae is a mycelium.
What is true of all viruses?
They are parasites of cells.
Which is a protoctist?
It is a single-celled organism that lives in pond water.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 8 marks. Write your answers on paper, then check them.
The variety of living organisms
Edexcel International GCSE Science (Double Award) 4SD0 · 8 marks · papermunch.org
Name ______________________________ Date ______________
Give three differences between plants and animals.[3]
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Any three: plant cells have cellulose cell walls, chloroplasts and large vacuoles and animal cells do not; plants photosynthesise and animals feed on other organisms; plants store starch and animals store glycogen; animals have nervous coordination and can move from place to place.
Describe how a fungus such as Mucor feeds.[3]
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Its hyphae release digestive enzymes on to the food it is growing on (extracellular digestion). The food is digested outside the fungus, and the soluble products are absorbed. This is saprotrophic nutrition.
Explain why viruses are not classed as living organisms by many biologists.[2]
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They are not made of cells and cannot carry out life processes on their own: they can only reproduce inside the living cells of a host.
Answers: The variety of living organisms
- 1. Any three: plant cells have cellulose cell walls, chloroplasts and large vacuoles and animal cells do not; plants photosynthesise and animals feed on other organisms; plants store starch and animals store glycogen; animals have nervous coordination and can move from place to place.
- 2. Its hyphae release digestive enzymes on to the food it is growing on (extracellular digestion). The food is digested outside the fungus, and the soluble products are absorbed. This is saprotrophic nutrition.
- 3. They are not made of cells and cannot carry out life processes on their own: they can only reproduce inside the living cells of a host.