Ecology

 

Key Definitions

Ecology: The study of how living things relate to each other and to their environment.

Biosphere: That part of the earth inhabited by living organisms, including land, ocean and the atmosphere in which life can exist.

Ecosystem: A community of living organisms interacting with one another and their environment within a particular area, e.g. deciduous woodland

Habitat: The particular place within the ecosystem where an organism lives and to which it is adapted

Population: A group of organisms of the one species living in part of an ecosystem

Producer: Any organism capable of making its own food from inorganic materials, e.g. green plants

Consumer: Heterotrophic organism that feeds on other organisms. It cannot make its own food

Detritus: Dead or decaying organisms

Detritus feeder: Organism that eats dead or decaying material, e.g. earthworm

Food Chain: A straight line sequence of what eats what in a community

Food Web: Made up of a number of interconnecting food chains

Niche: The functional role of an organism in an ecosystem, e.g. how it feeds, what it feeds on, what feeds on it

Humus: Is the decomposing organic matter in the soil

Adaptation: Method by which an organism or species becomes adjusted to its environment

 

Environmental Factors in the Ecosystem

Can be divided in three main groups – Abiotic, Biotic and Edaphic

Abiotic Factors

 These are the non-living features of an ecosystem that affect the community.

 They consist of the physical and chemical conditions, and they vary between ecosystems that are terrestrial or aquatic.

 They include: temperature, light intensity, air speed, water current, humidity, ­pH, dissolved oxygen, salinity, nitrate, phosphate and other plant nutrients

Abiotic factors………..

1. Light –needed for photosynthesis – crucial to all life in particular plants in the ecosystem
2. Temperature – influences the rate of all biochemical in an ecosystem

Also influences the rate of evaporation

1. Air – oxygen needed for photosynthesis, CO₂ for photosynthesis, wind causes physical damage, humidity is a measure of water vapour in the air – the less moisture in the air, the faster evaporation will occur
2. Water – water needed by all living organisms. Organisms that live in dry places are adapted to reduce water loss

 

Biotic factors

 These are the living features of an ecosystem that affect the other members of the community.

 These include: ­plants for food and shelter; predators; prey; parasites and pathogens; decomposers; competitors; and pollinators

Biotic Factors

 Competition – is the way in which organism compete with each other for resources

Examples…..

 Plants – compete with each other for light, water, space, nutrients, pollinators and seed dispersal

 Animals – compete with each other for food, water, territory and mate.

 Disease – microorganisms can cause disease which can weaken and kill larger organisms

 Humans – as hunters, farmers, fishermen, developer and polluter we influence the distribution of organisms

 

Edaphic factors

 The physical, chemical and biological characteristics of the soil that influence the community.

 The major edaphic factors are: available (soil) water, mineral content, pH, humus, soil texture and structure

Edaphic Factors

 Soil = rock, organic matter, sir water, dissolved minerals and living organisms

 The proportion of sand, silt and clay gives soils its different textures

 Texture influences properties like aeration (amount of air in soil), how much water the soil can hold (sandy soils hold very little water) and its drainage ability and finally ability to hold onto nutrients

 Organic Matter – comes from remains of dead organisms and animal wastes

 It’s broken down by detritus feeders into a black substance called humus

 Soil pH – is a measure of how acidic or basic a soil is. pH of soil affects the type of plants that can live in it

 

 

Energy flow through an Ecosystem

 Source of all energy on our planet is the sun

 Energy is then passed from one organism in an ecosystem to the next along a food chain

 Energy is “lost” as it passes along the food chain

Take for example the diagram above:

 Grass absorbs 10,000 kJs of energy from the sun – it uses 90% of this energy for its basic day to day metabolism and only 10% of the energy is stored in the grass

 The grass is eaten by the rabbit, but the rabbit only receives 1,000kJ’s of energy.

 Of this 1,000 kJ’s of energy, the rabbit uses 900kJ’s for its basic metabolism and the rest is stored in the body. (10%)

 The rabbit is then eaten by the fox – of the energy the rabbit got from the sun, the fox now only gets 10% of that – 100kJ’s

We can conclude a few points of information:

1. Only 10% of energy passes from one level of the food chain to the next
2. There is a limit to the length of the food chain due to the loss of 90% of the energy at each stage of the food chain

 

 

 

 

Trophic Levels

Feeding level: the position or energy level of a species in a food chain

Primary Producer – always a green plant

Primary Consumer – feeds off primary producer (herbivore)

Secondary Consumer – feeds off primary consumer

Tertiary Consumer – feeds off secondary consumer

 

Pyramid of Numbers

A Pyramid of Numbers represents the number of organisms at every level of a feeding chain – the wider the block of the pyramid, the more organisms found at that Trophic level

 There are two types of Pyramids of numbers

 

      &     

 The first pyramid shows a large number of grass plants, fewer rabbits than there are grass plants and even fewer foxes than rabbits

 The second pyramid shows one oak tree (primary producer) a large number of greenfly feeding on the one oak tree, fewer spiders than greenfly, fewer blackbirds than spiders and finally one hawk

 

Nutrient Recycling

Here there are two nutrients we’ve to took at, Carbon and Nitrogen, and how both of them are recycles

 

Carbon Cycle

 

 The air contains Carbon Dioxide CO₂

 All living things need carbon; it’s needed to make carbohydrates, proteins, fats etc

 Plants use CO₂ as carbon source (make glucose)

 Animals use plants as their source of carbon

 

 

 

 

How carbon is recycled….

1. Carbon is absorbed by plants for photosynthesis
2. Plants are eaten by animals – assimilation
3. When animals break down food in the process of respiration they release carbon in form of Carbon Dioxide
4. Animals die – their bodies are decomposed by microorganisms – carbon is released
5. Their bones and teeth are decomposed by weathering – carbon is released
6. Plants can also form fossil fuels – when these are burned, combustion, they release carbon

 

All of these steps ensure that there is a constant recycling of carbon in the biosphere

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Nitrogen Cycle