Edexcel IGCSE Biology - Variety of Living Organisms, Ecology and the Environment

Vocabulary flashcards covering key terms and descriptions from Module 1 (The nature and variety of living organisms) and Module 4 (Ecology and the Environment).

Plants

Multicellular organisms whose cells contain chloroplasts, are able to carry out photosynthesis, have cellulose cell walls, and store carbohydrates as starch or sucrose. Examples include flowering plants like maize (cereal) and peas/beans (herbaceous legume).

Animals

Multicellular organisms whose cells do not contain chloroplasts and cannot carry out photosynthesis, have no cell walls, usually have nervous co-ordination, are able to move, and often store carbohydrate as glycogen. Examples include mammals (humans) and insects (housefly, mosquito).

Fungi

Organisms unable to carry out photosynthesis, whose body is usually organised into a mycelium made from thread-like structures called hyphae containing many nuclei; they have cell walls made of chitin, feed by saprotrophic nutrition, and may store carbohydrate as glycogen. Examples include Mucor and single-celled yeast.

Hyphae

Thread-like structures containing many nuclei that make up the mycelium body structure of fungi.

Saprotrophic Nutrition

A mode of nutrition where organisms feed by extracellular secretion of digestive enzymes onto food material and subsequent absorption of the organic products.

Protoctists

Microscopic single-celled organisms; some have features like animal cells (e.g., Amoeba living in pond water), others contain chloroplasts and resemble plant cells (e.g., Chlorella), while pathogenic forms include Plasmodium.

Plasmodium

A pathogenic protoctist responsible for causing malaria.

Bacteria

Microscopic single-celled prokaryotic organisms that contain a cell wall, cell membrane, cytoplasm, and plasmids; they lack a nucleus but contain a circular chromosome of DNA. Most feed off living or dead organisms, though some photosynthesise.

Lactobacillus bulgaricus

A rod-shaped bacterium used in the production of yoghurt from milk.

Pneumococcus

A spherical bacterium that acts as the pathogen causing pneumonia.

Pathogen

An organism or agent that causes disease; pathogens include fungi, bacteria, protoctists, or viruses.

Viruses

Small non-living parasitic particles smaller than bacteria that reproduce only inside living cells; they lack cellular structure, have a protein coat, contain either DNA or RNA, and infect every type of living organism.

Tobacco Mosaic Virus

A virus that causes discolouring of tobacco plant leaves by preventing the formation of chloroplasts.

Carbon Cycle Stages

The processes that cycle carbon within ecosystems, including respiration, photosynthesis, decomposition, and combustion.

Nitrogen Cycle Bacterial Roles

The key functional groups of bacteria involved in cycling nitrogen: nitrogen fixing bacteria, decomposers, nitrifying bacteria, and denitrifying bacteria.

Greenhouse Gases

Atmospheric gases that contribute to the greenhouse effect, including water vapour, carbon dioxide, nitrous oxide, methane, and CFCs.

Deforestation Effects

Environmental impacts including leaching, soil erosion, disturbance of evapotranspiration and the carbon cycle, and disruption of the balance of atmospheric gases.