Environment

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

Pyramids of Numbers How many organisms are in a habitat

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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.

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.

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