1. Environment

2. Contents Energy Flow Through Ecosystems
Materials are Recycled in Ecosystems
Studying Ecosystems
Dynamics of Ecosystems
Human Activities Impose on the Environment

3. Pyramids of Numbers
How many organisms are in a habitat

4. Pyramids of Biomass How overall dry mass of organisms in a habitat
Always pyramid shape

5. Energy Transfer
Energy is absorbed up a food chain, but at each trophic level, this amount of energy decreases rapidly
1st: photosynthesis
2nd onwards: respiration
excretion
movement
transport

6. Carbon & Carbon Cycle Living organisms need carbon to:
make food (green plants photosynthesise)
make energy (through respiration)
make new cells for growth and repair

7. Living organisms need nitrogen to make proteins
Nitrogen Cycle
Living organisms need nitrogen to make proteins

8. Impact of Humans
Humans pose a huge threat to lives of animals, plants and their environment
Our impact is so great due to:
- technologies that change the world so quickly
- population increase
- consumption of natural resources, and waste

9. Human Population Growth
Humans can adapt to survive in almost all habitats and climates. The human population is increasing rapidly and is threatening the environment
The population will eventually be limited by these factors:
- food and water supply
- disease and pollution
- over-crowding
- sudden changes in climate

10. Urbanisation & Industrialisation
More and more people are moving into the cities. The effects:
- increased pollution due to traffic, energy consumption and waste production
- farmland is built on, land taken out of food production
- loss of natural habitats, as cities and roads are built
- rural communities and cultures dissolve as people leave to live in urban areas
Development of industries. The effects:
- non-renewable fossil fuels are used for energy
- release of greenhouse gases speeds up global warming

11. Effect of Fertilisers Intensive farming can damage the environment.
e.g.

12. Effect of Pesticides
Pesticides can harm larger organisms.
e.g.

13. Fishing & Forestry Fishing:
Unsustainability: the using up of resources faster than they are produced so that they will not continue in the future
e.g. North Sea Cod are over-fished so are reproducing slower than are being caught. Effect  population is heavily declining
Forestry:
Humans burn wood or clear land for farming  deforestation:
1) destroys habitats
2) causes soil erosion  barren land and flooding
3) causes pollution from combustion
4) increased levels of carbon dioxide as loss of photosynthesis

14. Pollution
Atmospheric: Caused by combustion, exhaust fumes, livestock, waste dumps
Effects:
- smoke, which damages air quality
- carbon dioxide and Methane, which cause climate change
- sulphur dioxide and nitrogen dioxide, which mix with rainwater to form acid rain
- carbon monoxide, which is poisonous to humans and animals
Water: Caused by deposition of substances into seas, lakes, rivers
- sewage and oil, which destroy habitats and kill animals
- fertilisers and pesticides, which damage ecosystems

15. Estimating Populations
Take samples: accuracy depends on
1) number of samples taken
2) method of collecting samples
3) proportion of total population sampled
Accuracy increases with number of samples
Dispersion:
random clumped uniform

16. Estimating Populations
S = S1 x S2 S3
S: total population
S1: 1st sample, total number captured, marked and released
S2: 2nd sample, total number captured
S3: 3rd sample, total marked number that are captured

17. Diversity
Depends on:
- number of species and abundance of each species in an ecosystem
Growth of population depends on:
- Abiotic factors
- Biotic factors
Index of Diversity:
d = N(N-1)/Σn(n-1)
d: index of diversity
N: total number of organisms of all species in area
n: total number of organisms of each species in area

18. Population Growth
Population of a species introduced to an environment grows as seen below:
This curve is named a Logistic or Sigmoid Growth Curve
1: Lag Phase
2: Rapid Growth Phase
3: Stable Phase (at end of this phase, population is stable)

19. Population Size Affected by:
Abiotic factors: temperature, water, pH, light, pollution etc.
Harsh environment: abiotic govern who survives
Mild environment: biotic govern who survives
Abiotic factors vary according to season
Reproduction rate increases with temperature so cycles:
More reproduction in summer
Less reproduction in winter

20. Population Size Affected by:
Food supply: if there is plenty of food, the population increases. However, if the population increases too quickly for the food to replenish, the population will decrease

21. Population Size Affected by:
Predation: populations of predators and prey depend on each other
prey population increases  predator population increases  prey population then will decrease  thus predator population decreases  prey population increases etc.

22. Population Size Affected by:
Disease: populations of host and parasite depend on each other
parasite population increases  host population decreases  parasite population then will decrease  thus host population increases  parasite population increases etc.

23. Summary Energy Flow Through Ecosystems
Materials are Recycled in Ecosystems
Studying Ecosystems
Dynamics of Ecosystems
Human Activities Impose on the Environment