Ecology

What is a 'habitat'?

- the environment in which an organism lives

What is a 'population'?

- the total number of organisms of the same species living in the same geographical area

What is a 'community'?

- the populations of all of the different species that live in the same habitat

What is an 'ecosystem'?

- the interaction of a community of biotic parts with the abiotic parts of their environment

What is the difference between 'biotic' and 'abiotic'?

biotic = living organisms
abiotic = non-living parts

What do organisms need to survive and reproduce?

- organisms require a supply of materials from their surroundings and from the other living organisms there

What 3 main factors do plants in a community or habitat often compete for?

- light
- space
- water

What 3 main factors do animals often compete with each other for?

- food
- mates
- territory

What is the term for how within a community, each species depends on other species for certain things; if one species is removed, it can affect the whole community?

interdependence

What makes a community be stable?

all the species and environmental factors are in balance => population sizes remain fairly constant

How does the level of competition affect organisms in a community?

- if a species is outcompeted, its population can fall => may even become extinct if numbers are insufficient to breed

How do moisture levels affect organisms in a community?

- both plants and animals need water to survive => if there are low levels of moisture, plants that are not adapted may die

How does wind intensity and direction affect plants?

- stronger winds may cause plants to lose water via transpiration

How do the carbon dioxide levels affect plants?

- a higher carbon dioxide concentration means plants can photosynthesise more

How do the oxygen levels in water affect aquatic animals?

- aquatic animals need dissolved oxygen from the water for respiration

3 types of adaptations?

• structural

• functional

• behavioural

How are camels STRUCTURALLY adapted to the hot and dry conditions of a desert?

• hump on their back which is a store of fat, metabolic reactions can be used to produce water from the fat

• mouth is leathery => allows camel to chew cacti

• long eyelashes → keep dust out of their eyes
  - camels can close their nostrils → keep dust out of their nose

• wide feet →prevents the camel from sinking into the sand

How are camels FUNCTIONALLY adapted to the hot and dry conditions of a desert?

- camels produce CONCENTRATED URINE and DRY FAECES => reduce water loss
- camels can tolerate very large changes in their body temperature => helps them to cope with the intense heat of the desert

What are different ways that some animals BEHAVIOURALLY adapted to survive in both hot and cool conditions?

• some animals are NOCTURNAL => avoid the heat of the daytime + these animals may also live in burrows underground during the day → keep cool and protects them from predators

• animals, eg. polar bears, hibernate during the winter to avoid the cold (the animal becomes inactive and all the body processes slow down)

• animals, eg. some birds, migrate south to warmer climates

How are some animals STRUCTURALLY adapted to survive the cold climate?

- very thick fur => provides insulation and reduces heat loss to the air
- fur on the soles of their feet, eg. the Arctic fox => reduces heat loss to the ice and the snow
- very small ears => reduces the overall surface area of the animal, eg. the Arctic fox => reducing heat loss
- white coat => effective camouflage (helps the animal to hunt its prey)

How are cacti adapted to live in the dry desert?

• very small leaves => reduce surface area for water loss, spines deter herbivores

• sunken stomata reduces transpiration

• extensive and shallow roots => absorb maximum water after rainfall

• cacti can store water in their stems (thick stems) => survive many months without rain

What are 'extremophiles'?

- organisms that live in environments with extreme conditions, eg. bacteria that live in deep sea vents

Give 3 examples of extreme conditions that an extremophile may be able to survive in?

- high temperature
- high pressure
- high salt concentration

What do feeding relationships show?

- flow of energy in a community

What do all food chains begin with?

• all food chains begin with a PRODUCER which synthesise glucose from sun energy

• plant or algae

(trophic level 1)

What is the general food chain?

producer => primary consumer (prey) => secondary consumer => tertiarry consumer => apex predator

Explain this predator-prey cycle graph.

- prey population increases => more food for predators => predator population increases => more of the prey are eaten => prey population falls => less food for predators => predator population decreases => prey population increases
- only true in a stable community

What are transects and quadrats used for?

• used by ecologists to determine the distribution and abundance of species in an ecosystem

How can we increase the accuracy of random sampling?

- using smaller divisions on quadrat

setting rule e.g only count squares with over 50% coverage

What is sampling along a transect used for?

What is a transect? How is sampling along a transect done?

• to investigate how the numbers of species change as we move across a habitat

• a transect is a line (tape measure)

• use a quadrat to count the organisms at intervals on the transect

How can we increase the validity of sampling along a transect?

- move the tape measure of rope further along in the horizontal direction => repeat the whole process

What is the importance of the carbon and water cycles?

- all materials in the living world are recycled to provide the building blocks for future organisms

How is carbon cycled?

1. photosynthesis by plants/algae remove co2 from atm

2. carbon used to make glucose, protein and lipids

3. respiration by all organisms releases co2 into atm

4. carbon passed through animals through ingestion/feeding/digestion

5. when plants, animals and algae die, decomposeres secrete enzymes to break them down (decomposers respire)

6. combustion/burning fossil fuels releases co2 into atm

What do decomposers do + what are they?

• reutrn mineral ions to soil

• return carbon to atmosphere as co2 when they respire, which is used by plants

• clean up environment by removing dead organisms and waste

• fungi and bacteria

How is water cycled?

1. evaporation of water from the earth’s surface which falls as rain and snow (precipitation)

2. absorbtion of plants via osmosis into roots

3. transpiration - evaporation of water from leaves of plants out of stomata

4. producition of urine, faeces and sweat by animals

5. respiration by animals and plants produces water

   • water is continuously evaporated and precipitated

optimum conditions for decay

1. warm

2. high oxygen availability

3. high moisture levels

What is the slurry used for from biogas generators

- used as a natural fertiliser for growing garden plants or crops
- compost is very rich in the minerals that plants need to grow (the decomposers return the mineral ions back to the soil)

molecules before and after decomposition

• large, insoluble

• small, solluble (can diffuse)

Why is it important to control the temperature of a compost heap? (stop it from getting too hot)

- if the temperature gets too high, the enzymes in the decomposers can denature

what gas is produced in biogas generator

methane

What is the method to investigate the effect of temperature on the rate of decay of fresh milk by measuring pH change?

1. label test tube milk and add 5ml + one drop phenolthalene

2. measuere 2ml of microbe solution and add to different test tub

3. add to waterbath, leave to equilibriate

4. after 5min, combine test tubes

5. time how long it takes to fo from bright pink to cream

6. repeat at different temps
   
   i.v. =effect of temp temperature
   d.v. = decay of milk
   c.v.. = volume of each component, type of milk

How can we increase the accuracy of the decompostion required practical?

- using several people to stop the timer when they believe that phenolthalene is gone colour => calculating a mean

What is the impact of a change in temperature on the distribution of species in an ecosystem?

- species that live in hot conditions, eg. a desert, will be more suited to the environment
- eg. the Desert fox lives in Africa and it has large ears which increase the fox's surface area, allowing it to lose heat more easily => the Desert fox would not be found in cooler places => as we move further north, the conditions get colder and we find the Arctic fox, with very small ears

- temperature shows geographic variation

What is the impact of a change in availability of water on the distribution of species in an ecosystem?

• in the dry desert, we find plants that are adapted to live here where the water is scarce

• => cacti are not found in regions where water is more plentiful,

• eg. a tropical rainforest (we instead find plants that are adapted to live in wetter conditions, such as ferns)

A large amount of untreated sewage entered the river. Many fish died. Untreated sewage contains organic matter and bacteria.
Explain why many fish died. (Exam Q)

- bacteria decay organic matter
- by digestion
- bacteria respire aerobically using oxygen
- which lowers the oxygen concentration in the water, leaving less oxygen for the fish
- so the reduced energy supply causes death of fish

What is 'biodiversity'?

- the variety of all the different species of organisms on earth, or within an ecosystem

Why is a higher level of biodiversity beneficial and important?

- a great biodiversity ensures the stability of ecosystems by reducing the dependence off one species on another for food, shelter and the maintenance of the physical environment, eg. decomposers break down the remains of dead organisms
- if the population of a species falls, it is less likely to affect the whole ecosystem

How is deforestation having a negative effect on biodiversity?

- tropical rainforests contain a very high level of biodiversity
- large areas of these forests are being destroyed to provide land, removing habitats at the same time

How do trophic levels represent the feeding relationships in an ecosystem?

Level 1: Plants and algae make their own food and are called producers.
Level 2: Herbivores eat plants/algae and are called primary consumers.
Level 3: Carnivores that eat herbivores are called secondary consumers.
Level 4: Carnivores that eat other carnivores are called tertiary consumers
- apex predators are carnivores with no predators

What is the role of decomposers?

- decomposers break down dead plant and animal matter by secreting enzymes into the environment
- small soluble food molecules then diffuse into the microorganism

What do pyramids of biomass represent?

- the relative amount of biomass (the living tissue of an organism, including proteins, lipids, and carbohydrates) in each level of food chain
- trophic level 1 is at the bottom of the pyramid

Why is biomass lost between the different trophic levels?

• not all ingested material absorbed, some egested as faeces

• some absorbed material is lost as waste, e.g co2

• water in respiration and urine

• lots of glucose used in respiration

How can we calculate the efficiency of biomass transfer as a decimal or percentage?

(gain in biomass / total intake) x 100 for a %

7 abiotic factors

1. temp

2. water/moisture levels

3. light intensity

4. wind speed/direction

5. soil ph + mineral ion conc

6. oxygen availability (aquatic)

7. CO2 conc (plants)

4 biotic factors

1. new pathogens

2. more competition between species

3. new predators arriving

4. availability of food

intraspecific competition

competition within a species

interspecific competition

competition within different species

reproducible

if someone else does sample + gets similar results

repeatable

you repeat and get similar estimate

valid

able to answer the question being asked accurately

how to do random quadrat sampling

1. split study area into grid with coordinates using two tape measures

2. randomly choose which coordinates to sample using random number generator

3. place quadrat at the coordinates and count the number of indivicuals

4. repeat at least 20 times

5. from this data, calculate the mean

6. mean number of individuals in quadrat X area of field = estimate of populatoin

what to do before random quadrat sampling

establish inclusion criteria e.g count half or not?

3 environmental changes effecting distribution of species in ecosystem, 3 causes

• temp

• water availability

• composition of atmospheric gas

  • seasonal

  • geographic

  • human intercation