topic 4 - variety of living organisms

Question 1

what is a eukaryote?

Answer 1

any cell or organism that contains a clear and defined nucleus e.g. Plants, animals, fungi and protoctists

Question 2

what is a prokaryote?

Answer 2

a single cell organism that lacks a nucleus and other membrane-bound organelles e.g. bacteria

Question 3

common features of a eukaryote: plants

Answer 3

• multicellular
• chloroplasts to carry out photosynthesis
• have cellulose walls
• store carbohydrates as starch or sucrose
• e.g. flowering plants, peas, beans

Question 4

common features of a eukaryote: animals

Answer 4

• multicellular
• nervous coordination to move from one place to another
• store carbohydrates as glycogen
• e.g. mammals, insects

Question 5

common features of a eukaryote: fungi

Answer 5

• organised into mycelium made from thread-like structures called hyphae, which have a lot of nuclei
• walls made of chitin
• feed by saprotrophic nutrition -extracellular secretion of digestive enzymes onto food material + absorption of organic products
• store carbohydrates as glycogen
• e.g. Mucor, yeast

Question 6

common features of a eukaryote: protoctists

Answer 6

• microscopic single-celled organisms
• e.g. Amoeba, which lives in pond water - has features of an animal cell
• e.g. Chlorella, which has chloroplasts - has features of a plant cell
• e.g. Plasmodium - pathogenic protoctists - causes malaria

Question 7

common features of a prokaryote: bacteria

Answer 7

• microscopic single-celled organisms
• have a cell wall, cell membrane, cytoplasm and plasmids
• lack a nucleus, but have a circular chromosome of DNA
• some can carry out photosynthesis but most feed off other living or dead organisms
• e.g. Lactobacillus bulgaricus - used in milk + yoghurt
• e.g. Pneumococcus - pathogen causing pneumonia

Question 8

what is a pathogen?

Answer 8

an organism that causes disease to its host. it can be fungi, bacteria, protoctists or viruses

Question 9

common features of a pathogen: viruses

Answer 9

• not living organisms
• very small, smaller than bacteria
• parasitic - can only reproduce inside living cells
• infect every type of organism
• variety of shapes and sizes
• no cellular structure - have a protein coat and contain one type of nucleic acid, either DNA or RNA
• e.g. tobacco mosaic virus - prevents formation of chloroplasts in tobacco plants
• e.g. influenza virus - causes the flu
• e.g. HIV virus causes AIDS