TOPIC 5: ECOLOGY and EVOLUTION

5.1.1

• Species: a group of organism that can interbreed and produce fertile offspring

• Habitat: the environment in which a species normally lives or the location of a living organism

• Population: a group of organisms of the same species who live in the same area

• Community: a group of populations living and interacting with each other

5.1: Communities and ecosystems

• Ecology: the study of relationships between living organisms and between organisms and their environment

• Ecosystem: a community and its abiotic (non-living; temperature, humidity, wind, rainfall etc.) environment

5.1.2: Autotroph/heterotroph

Autotroph: an organism that synthesizes its organic molecules from simple inorganic substances

Heterotroph: an organism that obtains organic molecules from other organisms

5.1.3: Consumers, detritivores, saprotrophs

Consumers: an organism that ingests other organic matter that is living or recently killed.

Detritivore: an organism that ingests non-living organic matter.

Saprotrophs: an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion, examples; bacteria and fungi

M09/4/BIOLO/SP2/ENG/TZ2/XXDefine the terms species, population and community.Species: Population:. Community: [3]

N08/4/BIOLO/SP2/ENG/TZ0/XX+ Define the term ecosystem. [1]

5.1.4: Food Chain

Producer → Primary

consumer → Secondary consumer → Tertiary

consumer

Oak treeQuercus → Caterpillar

Archips → Spotted towheePipilo → Cooper’s Hawk

Accipitor

Sea lettuce Ulva → Finger limpet

Collisella → Rock crabCancer → Giant Octopus

Octopus

Saguaro cactus

Carnegiea → JackrabbitLepus → Rattlesnake

Crotalus →Red-tailed

HawkBeauteo

Describe what is meant by a food chain using an example with four named organisms. [4] M11/4/BIOLO/SP2/ENG/TZ2/XX

food chains describe the feeding relationships between species;arrows show (one) path of energy flow in an ecosystem / energy flow described;food chain with arrows pointing in the correct direction;producer first step in chain;three other named organisms making a realistic food chain; [4 max]Accept explicit common names exact enough to identify the food source e.g. Oak nottree, sparrow not bird, rye grass not just grass, etc.

N08/4/BIOLO/SP2/ENG/TZ0/XX/M+ Examples must be based on a realistic ecosystem. Award [1] for each of the following clearly drawn and correctly labelled. a chain (not in a web or pyramid) which includes the names of four organisms and three linkages in a logical feeding order/sequence; each linkage symbolized by an arrow () showing the direction of energy flow; autotroph/producer and consumer labels correctly associated with organism; all three additional consumer labels correctly associated: primary, secondary and tertiary; [4 max]

5.1.5: Food web

Describe what is meant by a food chain and a food web. [6] N10/4/BIOLO/HP2/ENG/TZ0/XX

Accept examples of the points below, provided that the terms underlined areclearly identified. Accept only named examples (latin or common names) fromnatural ecosystems only. Do not award marks for general names such as “fish”or “tree”.food chain shows transfer of nutrients/energy in an ecosystem / arrows from onetrophic level to the next in examples;between different trophic levels / shown in a correct chain or web;starting with a producer;followed by at least two levels of consumers / shown in a correct chain or web;food web is the (branched) interaction of multiple food chains / cross arrows inexamples;using (multiple) producers as a source;transferring nutrients/energy to consumers from different food chains;same consumer could be at different trophic levels in a food web; [6 max]

M07/4/BIOLO/SP2/ENG/TZ2/XX The diagram below shows a simplified food web for a lake.

State the initial energy source for the above food web. [1]Define the term trophic level. [1]

Deduce the trophic level of the immature game fish.[1]

In the food web shown, identify one heterotroph and one autotroph.heterotroph:

5.1.6: Trophic level

1st trophic level

2nd trophic level

3rd trophic level

4th trophic level

5th trophic level

Explain, using an example of a food chain, how trophic levels can be deduced. [4]M11/4/BIOLO/SP2/ENG/TZ1/XX

diagram of food chain showing at least three organisms and two linkages witharrows showing direction of energy flow;trophic level is a step/position in the movement/flow of energy through anecosystem;(in a field situation) observe which organisms eat each other;producer/name from example (first trophic level) does not eat otherorganisms/captures energy through photosynthesis;primary consumer/name from example (second trophic level) feeds on producers;secondary consumer/name from example (third trophic level) feeds on primaryconsumers; [4 max]Since the command term is explain, the answer must be explicit to gain markingpoints d–f. Named examples for producer and consumers in diagram orexplained example must represent a coherent food chain. Reject chains usinggeneral names such as fish or tree or grass. But, accept sardine or oak.

(a) light penetration is required for photosynthesis;plants/phytoplankton/photosynthetic organisms are the base of many aquatic foodchains;allows interacting organisms to find one another (e.g. predator-prey relationship,courtship);allows interaction with the physical environment (e.g. finding shelter); [2 max](b) (i) light / sunlight [1](ii) the feeding level/position an organism occupies in a food chain [1](iii) secondary consumer [1](iv) heterotroph: immature game fish / trout / pike / shad / zooplankton;autotroph: phytoplankton; [1 max]Two correct answers needed for [1].

5.1.9: Light energy

• State that light is the initial energy source for almost all communities.

5.1.10: Energy Flow

5.1.11: Energy transformations

5.1.12: Pyramid of Energy

STATE: Energy transformations are never 100% efficient

N06/4/BIOLO/SP2/ENG/TZ0/XX The diagram below represents an energy pyramid and four trophic levels.

Identify the trophic level of the organisms indicated below.I: IV[2](ii) Calculate the approximate amount of energy in kilojoules transferred in m–2 yr–1from trophic level I to trophic level II.______________________kJ

M08/4/BIOLO/SP2/ENG/TZ1/XX+ Explain the reason for the shape of a pyramid of energy. [3]

(the shape of pyramid) shows energy lost from base to top of pyramid/at eachtrophic level;(because) energy is used/released through cell respiration/heat/movement (at eachtrophic level);not all tissues are eaten i.e. bone/hair/cellulose/excretion/undigested/die;less energy available at each trophic level / only 10- 20% passed on so each levelis (80-90%) smaller than the preceding / a diagram must show the approximatechanges in levels; [3 max]

5.1.13: Energy and nutrients

5.1.14: DecomposersSTATE: Saprotrophic bacteria and fungi (decomposers) recycle nutrients

N08/4/BIOLO/SP2/ENG/TZ0/XX+ Outline the role of decomposers in recycling nutrients.

[2]

break down/digest dead organic matter; (do not accept “feed”) unlock/produce inorganic nutrients/soluble compounds/ions; (inorganic nutrients) assimilated by living organisms / an example of this; bacteria/fungi/saprotrophs; [2 max]

State the names of the processes that(i) convert carbon dioxide into organic compounds in pond weeds and algae.[1]

convert organic compounds in pond weeds, algae and primary consumers intocarbon dioxide. [1]

Draw arrows on the diagram above to show how the saprotrophs obtain carbon.(ii) Explain the role of saprotrophs in recycling carbon.[1][2](c) Draw a box on the diagram in an appropriate position, labelled organic compounds insecondary consumers. Draw arrows to show the links between secondary consumers andother parts of the carbon cycle.