D1. Ecology

(1)

(2)

Ecosystems

• _{Ecosystem: the inter-relationship of living}

(biotic) and non-living (abiotic) elements in a specific area.

• _{Two major factors influence ecosystems:}

(3)

Population

• _{A group of individuals of the same species that occupy}

the same habitat at the same time.

Bee hive of a giant honey bee.

The population of a honey bee is easy to define but it might be harder to other

species where

(4)

Community

• _{The organisms of all species that live in a}

particular area.

(5)

Habitat

(6)

(7)

Ecological Niche

• _{All conditions and resources required for an}

organism to survive, reproduce and maintain a viable population.

• _{For this swallowtail}

(8)

Random Sampling

• _{Form a grid using two tape}

measures at right angles

• _{Obtain random co-ordinates}

using random numbers

generated by a calculator and place the quadrat at those

coordinates.

• _{Random sampling increases}

(9)

Quadrats:

Three considerations before

selecting a quadrat

• _{Appropriate size (depending on the size and}

number of the organisms)

• _{Number of sample quadrats to record within}

the study area – the larger the number the more reliable the results

• _{Need to use random sampling to achieve}

(10)

Food Chains

• _{Food chains are used to show which animal}

eats another animal. The “→” means “is eaten by”.

(11)

Grass  Rabbit → Fox

- _{The food chain show us that energy is}

passed from the grass to the rabbit when the rabbit eats the grass.

- _{The food chain also shows us that energy is}

passed from the rabbit to the fox as the fox eats the rabbit.

(12)

Labelling the food chain

Each stage of the food chain can be given a different

name. Food chains always start with plants – they are known as the producer. Plants are always eaten by

herbivores or omnivores and herbivores and omnivores are always eaten by carnivores.

Tree → Caterpillar → Blackbird Producer Herbivore Carnivore

(13)

Trophic Levels

• _{Food chains can also be labelled by their trophic}

level. The first organism in the food chain is always trophic level 1, the second organism is always trophic level 2, etc.

e.g. Pond weed  Water skater → Toad

(14)

Pyramid of numbers

To show how energy is passed through a food chain we can draw a diagram called a pyramid of numbers.

(15)

Drawing a pyramid of numbers

• _{When drawing a pyramid you always start with the}

bottom of the food chain – this forms a rectangle block at the bottom of the pyramid, so in our

example it would represent 1000 blades of grass.

• _{The 3 rabbits are represented by a smaller rectangle}

above

• _{The one fox is the top layer which is represented by a}

(16)

(17)

Pyramids of number don’t always look like a

pyramid and aren’t always a good representation of the amount of energy in the food chain

For example one tree supporting many caterpillars

(18)

Pyramids of Biomass

• _{Pyramids of biomass are}

rarely top heavy as they take into account of the mass of the organisms if they were dried and weighed together.

• _{They are therefore a more}

accurate measure of the energy in a food chain

(19)

• _{For example, the mass of the tree might be}

3000 Kg

• _{then all the caterpillars on the tree might}

weigh 10Kg

(20)

Drawing a pyramid of biomass

• _{When drawing a pyramid of biomass you always start}

with the bottom of the food chain – this forms a rectangle block at the bottom of the pyramid and

represents the mass of that organism, e.g. 3000 Kg of Oak

• _{The mass of the caterpillars would be represented by}

the next step up in the pyramid.

• _{The one fox is the top layer which is represented by a}

(21)

Pyramids of Energy

• _{Pyramids of energy show how much energy}

there is present at each trophic level.

• _{To calculate pyramids of energy material}

from each trophic level has to be burned and then measured using a calorimeter.

• _{Only small samples can be used to build}

(22)

(23)

Describe an experiment to investigate the energy content in a food sample.

• _{Burn the food sample completely under a}

calorimeter

• _{Make sure there aren’t any draughts}

• _{The larger the calorimeter the smaller its}

surface area to volume ratio, so the less likely it will cool down.

(24)

Where does the energy come from to

supply energy to food chains?

• _{The energy comes from the sun!}

• _{Green plants capture a small amount of light}

energy and use it in photosynthesis to make sugar. This sugar is then used to make all

(25)

Energy is lost at each stage in the food

chain

• _{10% of energy is transferred between trophic}

levels – 90% of energy is lost through

respiration and urine and faeces.

• _{This means that efficient food production can}

(26)

• _{Efficiency of food production can also be}

improved from animals by limiting their

respiration by limiting their movement and controlling their temperature.

• _{By limiting movement and controlling their}

temperature we limit the energy lost in respiration.

(27)

Meat-eating and energy efficiency

• _{It is far more efficient for humans to eat}

cereals such as wheat and barley rather than to use the cereals to feed cattle and then to slaughter the cattle for beef.

• _{This is because the energy in the beef has}

already passed through two steps by the time it gets to humans, and at each step the

(28)

• _{When we eat plants such as cereals, vegetables or fruit, the}

(29)

• _{When we eat plants such as cereals, vegetables or fruit, the}