Biology iGCSE Edexcel

Name some eukaryotic organisms

• plants

• animals

• fungi

• Protoctists

describe common features of plants

• multicellular organisms

• cells contain chloroplasts and are able to photosynthesize

• have cellulose cell walls

• store carbohydrates as starch/sucrose

examples: cereal, herbaceous legume, plants

describe common features of animals

• multicellular organisms

• no cell walls

• nervous coordination

• able to move

• store carbohydrates as glycogen

examples: mammals, insects etc

describe common features of fungi

• organized in mycelium from structures called hyphae

• some are single celled

• walls made of chitin

• feed by saprotrophic nutrition - feed by extracellular secretion of digestive enzymes onto food material and absorption of organic products

• may store carbohydrates as glycogen

examples: mucor, yeast

describe common features of protoctists

• microscopic single celled organisms

• some are like amoeba like a animal cell

• some are like chlorella like a plant cell

example: plasmodium responsible for malaria

what is a prokaryotic organism example?

bacteria

describe the structure of bacteria

• micrscopic single celled organisms

• have cell wall

• cell membrane

• cytoplasm

• plasmids

• no nucleus but have a circular chromosome of DNA

• some carry out photosynthesis but most feed off living or dead organisms

examples: lactobacillus bulgaricus - used in yogurt production, pneumococcus - spherical bacterium that acts as a pathogen causing pneumonia

define pathogen

A pathogen is an organism, such as a virus, bacterium, or fungus, that causes disease or illness in its host.

describe the structure of a virus

• non living organisms

• small particles smaller than bacteria

• parasitic and can reproduce inside living cells

• infect every type of organism

• have a wide variety of shapes and sizes

• no cellular structure

• have a protein coat and contain one type of nucleic acid either DNA or RNA

examples: tobacco mosaic virus - causes discoloring of leaves of tobacco plants by preventing formation of chloroplasts, influenza - causes flu and HIV virus that causes AIDS

levels of organization list

organelles —> cells —> tissues —> organs —> organ systems

define organelles

part of cell with a particular function

define cells

basic structural unit of living organisms

define tissues

collection of similar cells working together to perform a function

define organ

structure in a body of an animal or plant that is a collection of different tissues working together to perform a function

define organ system

collection of different organs working together