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Summary ecosystems a level biology notes

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summary notes on the topic of ecosystems of module 6 of a level biology, covering every part of the specification. diagrams included. source: kerboodle a level biology textbook

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  • April 30, 2024
  • 16
  • 2023/2024
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A-LEVEL BIOLOGY

ECOSYSTEMS
ECOLOGY




Introduction

,Ecology: study of relationships between organisms and their environment

Biome: large naturally occurring community of flora and fauna occupying a major habitat

Ecosystem: living organisms interacting with one another in a defined area, and also the

physical factors present in that region.

Vary in size :

Eg. tiny bacterial colony, entire biosphere of Earth

Dynamic: constantly changing as a result of living organisms and environmental conditions

Factors

Biotic: (living) eg. size of population and competition for a food source

Interactions btw organisms living/once lived

Involve intraspecific/interspecific competition

Abiotic: (non-living/physical) eg. amount of rainfall, yearly temperature range

● Plants develop strategies to cope with diff light intensities

Eg. low light = larger leaves

Photosynthetic pigments requiring less light

Reproductive systems operating only when optimum light availability

● Changes in temperature due to changing seasons trigger migration + hibernation. In

plants, triggers leaf fall, dormancy and flowering

● Lack of water = plants wilt as as cells not turgid + upright

● Aquatic ecosystems: fast flowing cold water has high concentrations of oxygen

Water too warm/ Flow rate too slow: drop in oxygen concentration




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, Waterlogged soils: air spaces btw soil particles filled with water = reduces oxygen

availability

● Edaphic (soil) factors : diff soil types have diff particle sizes

- Clay : fine particles, easily waterlogged, clumps when wet

- Loam: retains water but not waterlogged

- Sandy: coarse,well-separated particles for free draining, no water retained, easily

eroded

BIOMASS TRANSFER

All organisms require source of energy to perform functions needed to survive

Sun: source of light energy converted into chemical energy by photosynthesis, which is

then transferred to other non-photosynthetic organisms as food.

Food chains + webs show transfer of biomass (mass of living/dead material) through

organisms

Each stage = trophic level

1st: producer (photosynthetic)

2nd: primary consumer eating a producer (herbivore)

Subsequent levels: consumers that obtain energy by feeding on other organisms

Rarely 4+ trophic levels: not sufficient biomass + stored energy left to support any further

organisms

Decomposers break down dead organisms, releasing nutrients back into the ecosystem

Pyramid of numbers: represents number of organisms at each trophic level

Producers always at bottom with subsequent levels added above




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