IB Study Guide 1: Communities and Ecosystems

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Biology
IB Study Guide 1: Communities and Ecosystems
5.1 Communities and Ecosystems (Core)
5. 1. 1Define species, habitat, population, community, ecosystem, and ecology.
Species – A species is a group of organisms with similar characteristics, which can interbreed and produce viable, fertile offspring.
Habitat – A habitat is the environment in which a species normally lives or the location of a living organism.
Population – A population is a group of organisms of the same species, who live in the same area at the same time.
Community – A community is a group of populations living together and interacting with each other in an area.
Ecosystem – An ecosystem is a community and its abiotic environment.
Ecology – Ecology is the study of relationships in ecosystems – both relationships between organisms and between organisms and their environment. 5. 1. 2Distinguish between autotroph and heterotroph.

Autotrophs are organisms that synthesize their own organic molecules (food) from simple inorganic substances. More commonly known as producers, autotrophs make their own food. In most communities these producers create their own food through the process of photosynthesis. Meanwhile heterotrophs are organisms that obtain organic molecules (food) from other organisms. There are three different types of heterotrophs. The heterotrophs are represented by the consumers in a community, and can be found on the top of the food chain with the tertiary consumers. 5. 1. 3Distinguish between consumers, detrivores, and saprotrophs. There are three types of heterotrophs including consumers, detrivores, and saprotrophs. Consumers are organisms that ingest organic matter that is living or recently killed. Consumers are also split into three categories: primary, secondary, and tertiary consumers. Primary consumers directly ingest producers. Secondary consumers consume primary consumers as well as producers. Tertiary consumers are at the top of the food web and can consume any other consumers or producers. Detrivores ingest dead organic matter. And saprotrophs live on or in dead organic matter, secreting enzymes into it and absorbing the products of digestion. 5. 1. 4Describe what is meant by food chain, giving three examples, each with at least three linkages (four organisms).

A food chain is visual representation of sequences of trophic relationships, where each member in the sequence feeds on the previous one. Trophic relationships are very important – where one population of organism feeds on another population. Example: Producer Primary consumer Secondary consumer Tertiary consumer

5. 1. 5Describe what is meant by a food web.
A food web is a diagram of all the feeding relationships in a community. The arrows indicate the direction of flow of energy. 5. 1. 6 Define trophic level.
Trophic level – The trophic level of an organism is its position in the food chain. Examples of this are producers, primary consumers, secondary consumers, and tertiary consumers. 5. 1. 7Deduce the trophic level of an organism in a food chain or food web.

Photosynthetic organisms including plants, or all autotrophs, are producers in a food web. Primary consumers are organisms that eat only the producers. Secondary consumers then eat the primary consumers. And in turn the tertiary consumers eat the secondary consumers. 5. 1. 8 Construct a food web containing up to 10 organisms, using appropriate information.

5. 1. 9State that light is the initial energy source in all communities.
In almost all communities the producers make organic matter through the process of photosynthesis. This making light is the initial energy source for the whole community. Producers convert light energy into the chemical energy of sugars and other organic compounds 5. 1. 10 Explain the energy flow in a food chain.

Sunlight gives energy in organic matter to producers through the process of...
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