P2B - Ecology 4

Habitat

Habitat

The environment in which an organism lives

• elephants habitat is grassland

Population

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

Community

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

Biotic and Abiotic

• Biotic: All living organisms in an environment

• Abiotic: All non-living parts of an environment (including water/minerals in soil)

Ecosystem

Both the biotic and abiotic parts of an environment and how they interact

Resources that organisms compete for

• Plants compete for light, space, water and mineral ions in the soil.

• Animals compete for food, water, mating partners and territory.

Interdependence

All of the different species in a community depending on each other. If a species disappears from a community then this can affect the whole community.

• every animal depends on other living organisms for food (carnivores/herbivores)

• some living organisms provide shelter (tree sheltering animals from sun)

• plants depending on animals (bees spreading pollen/birds spreading seeds)

Stable community

Populations of the different species remaining fairly constant = in balance with each other and with the abiotic resources

V1 - competition and interdependence

Biotic factors

• Availability of food:

  • food falls = organism number falls

• New predator:

  • prey species falls

  • effects existing predator if competing for the same prey

• Competition between species:

  • species outcompeted then its population can fall so much = numbers are no longer sufficient to breed = extinct

• New pathogens:

  • infectious disease spreads = wipes out species population

Abiotic factors

• Light intensity:

  • major effect on plants since they all need it for photosynthesis

  • low LI = rate falls = slow growth = herbivores don’t have enough food

• Temp:

  • temp change = distribution of species change

  • animals migrate and plant species might disappear from the area

• Water:

  • plants/animals need it to survive

  • species adapt to low water levels

• pH and mineral soil content:

  • plants can’t grow on too acidic/alkaline soil

  • certain minerals (nitrate) is needed for amino acids and protein

• Wind intensity and direction

  • strong winds blowing inland from sea = plants lose water

  • plants in sand dunes adapt to reduce loss

• CO2:

  • needed for photosynthesis = CO2 fall means rate decreases

• O2:

  • needed for aerobic respiration

  • oxygen level in air stays constant but dissolved oxygen in water can fall on hot days = harmful to aquatic organisms

v2 - Biotic and Abiotic factors

Structural, functional and behavioural adaptations

• Structural are adaptations of body shape/structure

• Functional are adaptations to the body functions of an organism

• Behavioural are adaptations to the animals lifestyle/behaviour

Camel adaptations

Adapted to hot and dry desert conditions.

Structural adaptations:

• Hump stores fat

  • allows heat loss from other body parts = reduces water loss from sweating

  • metabolic reactions used to make water from fat

• Hump and thick coat on body’s upper surface

  • insulates top from suns heat = reduces water loss from sweating

• Leathery mouth

  • chew thorny desert plants = good water sources

• Long eyelashes and can close nostrils

  • keep dust out of eyes and nose

• Wide feet

  • prevent sinking into sand

Functional adaptations:

• Produce concentrated urine and dry faeces

  • reduce water loss

• Tolerate very large body temp changes

  • cope with deserts intense heat

Kangaroo rat adaptations

Lives in desert - Behavioural:

• nocturnal = active at night = avoid daytime heat

• during day they live in underground burrows = cool + predator protection

Arctic fox adaptations

Structural

• Very thick fur = insulation and reduces heat loss to air

• Fur on feet soles = reduces heat loss to ice/snow

• Very small ears = reduces SA of fox = reduces heat loss

• White coat is camouflage = helps for hunting pray

Cactus adaptations

Adapted to dry desert conditions:

• some have very small leaves to reduce water loss

• other have no leaves at all, only spines

• spines protect cactus from animals

• extensive and shallow roots = catch water after rainfall before it evaporates/sinks into ground

• store water in stem = survive many months without rain

Extremophiles and example + its adaptations

Organisms adapted to extreme conditions.

• On the sea bed, a deep sea vent has bacteria that can:

  • live in high temp/pressures

  • live in very high salt concs

v3 - Adaptations

Producer key points

• green plant at the start of all food chains

• synthesise complex molecules (e.g make glucose by photosynthesis)

• source of all biomass in a community:

  • molecule like glucose is biomass, which is passed down the food chain to other organisms

Primary, secondary and tertiary consumers

• primary - organisms that eat producers and are eaten by a secondary consumer

• secondary - organism that eats a primary consumer

• tertiary - organism that eats a secondary consumer

Graph of predator and prey populations in a community explained

Number of (any) predators and (any) prey rise and fall in cycles BUT this is only true in a stable community:

• rabbit population may rise due to warm summer with plenty of grass to eat

• this means more offspring survive = pop increases

• foxes have more rabbits to eat = fox pop also rises

• more foxes = more rabbits will be eaten = rabbit population falls

• less rabbits = less food for foxes = fox pop falls

• more rabbits can survive and reproduce = rabbit pop increases

• fox have more food = fox pop rise

If a drought happened or new predator arrived and community is no longer stable, then predator-prey cycles would change.

v4 - Food chains and predator-prey cycles

2 Sampling types and def of sampling

How scientists determine number of organisms in an area:

• random sampling

• sampling along a transect

Random sampling:

Hypothesis: “fewer ferns are found in light conditions than dark”

Hypothesis = We are comparing the numbers of organisms in different areas using a quadrat:

Measuring ferns in light conditions:

1. Place quadrat (wooden/plastic square), on the ground at random locations across the area, using random numbers to select the diff locations.

2. Count the numbers of each organism inside the quadrat.

   • can be used on plants/slow-moving animals

3. Move quadrat to a diff random location and repeat step 2.

4. Repeat till you sampled a large number of random locations.

   • large number = more likely to get valid results

   • placed once = doesn’t accurately represent whole area

Measuring ferns in dark conditions:

1. Repeat experiment

2. Find that hypothesis is correct - fewer ferns found in light conditions.

3. Estimate the total population size of a species in an area:

   • total pop size = total area/area sampled * number of organisms of that species counted in sample

Sampling along a transect:

Hypothesis: “species of plants that we find on a sand-dune change as we move inland from the sea”

Hypothesis: Investigating whether the numbers of species change as we move across a habitat.

• Transect is a line like a tape measure/rope, placed so it runs across the habitat

1. Place tape measure on the dune running from the beach inland.

2. Place first quadrat at the start of the transect and count diff plants in it.

   • on beach theres probably no plants

3. Move quadrat closer inland by a set distance (e.g 2m) and count again. Repeat as we move further inland.

4. Carry out transect many times for valid results - move tape measure along and repeat the whole process.

v6 - sampling organisms

RP9: Sampling organisms - daisy field

1. Place two 20m tape measures at right angles.

2. A group of 3 pupils need 2 bags with the numbers 1 to 20.

3. First pupil removes number from bag. Imagine its 8. Student moves up to 8m point on one of the tape measures.

4. Second student selects number 12 and moves to 12m on the other tape measure

5. Third student places a 0.5×0.5m² quadrat on the 8×12m point.

6. Record number of daisies. Repeat this till you have 10 samples.

   • imagine they counted 300 daisies across the 10 quadrats

RP9: Estimate total pop of daises in the whole field

Estimate total pop of daises in the whole field:

• total pop size = total area/area sampled * number of organisms of that species counted in sample

• total area = 20m x 20m = 400m²

• area sampled = 0.5 × 0.5 (quadrat) ×10 (times thrown) = 2.5m²

• daisies counted = 300

• 400/2.5 × 300 = 48 000

RP9: Estimate total pop of daises in the whole field - issues

Estimate = may not represent whole area:

• might be regions within area with much higher or lower number of daisies than the average.

• if we think this is the case, increase the number of throws to cover a greater % of the area

RP9: measure effect of a factor on the distribution of a species

• this case we are looking at light intensity effect on daisy distribution

Field of daises containing a tree - use transect line to see how daisy number changes from the tree outwards

1. Place tape measure at the tree

2. Use quadrat to count daisy number at the start of the transect and record light intensity at this point - using light metre or an app

3. Move quadrat 1m down and repeat measurements. Continue all the way down the tape measure.

   • may see more daisies as you move further from the tree since under the tree theres a lower light intensity and plants need light to photosynthesize

   • a tree will also absorb a lot of water/minerals from the soil

   • LI may not be the only abiotic factor affecting daisy count

v6 - RP9: Sampling organisms

Finding mean with anomalous results

• anomalous means ones that don’t fit the pattern

• these should NOT be included in the mean

Mode of 1, 3, 4, 5, 8, 11

There is no mode - most often appearing number

v7 - Mean, median and mode

Carbon cycle 2 key ideas

1. Photosynthesis (is the only way that) brings carbon into the cycle

   • cycle always starts with CO2 in the atmosphere

2. Aerobic respiration returns carbon back to the atmosphere

   • every living organism carries out respiration

Carbon cycle steps

1. CO2 in the atmosphere is taken in by plants and algae through photosynthesis

   • the carbon is used to make carbohydrates, fats and proteins which make up plant and algae

2. Plants and algae respire, so some carbon is released back to the atmosphere as CO2.

3. Plants and algae can be eaten by animals. These animals can be eaten by other animals

   • carbon that was in the plants becomes part of the carbohydrates, fats and proteins in the cells of animals

4. Animals respire, so some carbon is released back to the atmosphere as CO2.

5. Animals release waste products like faeces and eventually all animals and plants die.

6. Now carbon is in waste products and dead remains that are broken down by decomposing microorganisms like bacteria and fungi. When they respire, carbon is returned to the atmosphere as CO2.

Importance of decomposers in the carbon cycle and issues they face

• important since they return carbon AND release mineral ions to the soil

• under certain conditions (oxygen lack), they can’t function effectively = carbon in dead remains can be slowly converted to fossil fuels

Consequences of decomposers not functioning

• overly many millions of years, a large amount of carbon has been trapped underground as fossil fuels

• Combusting fossil fuels is releasing a large amount of CO2 back into the atmosphere

v8 - Carbon cycle

Water cycle in ecosystems

1. Energy from the sun makes water evaporate from the sea’s surface

2. Vapour travels into the air and cools down, condensing to form clouds

3. Water in clouds falls to the ground as precipitation (rain,snow,hail,sleet)

   • all precipitation forms contain fresh water with no salt contained

4. When water hits the ground:

   • some evaporates back to the atmosphere as vapour

   • some passes through rocks to form aquifers

   • a lot forms rivers/streams (which eventually drain back to the sea).

Water cycle in living organisms

• Plants take up water in their roots - moves up xylem and passes out stomata as vapour = transpiration.

• Animals take in water through food/drink - release in urine, faeces and exhalation

v10 - Decomposition

Decomposition by gardeners

1. Gardeners put dead plant material (like grass) onto the compost heap

2. Over time, bacteria and fungi decompose the plant material and produce compost.

3. They use compost as a natural fertiliser since it’s very rich in minerals that plants need to grow.

Optimal conditions for decomposition and important things to consider for each condition (issues)

• Warmer temp = happens faster since decomposers use enzymes to break down plant materials. Enzymes work faster in warm conditions.

  • compost heaps are warm since decomposers release energy when aerobically respiring

  • if compost gets too hot, enzymes in decomposers can denature and decomposers can die

• Water amount = decomposers work faster if compost is moist since many chemical reactions in decay require water

  • compost heap must not dry out

• Oxygen amount = decomposers aerobically respiring which requires good oxygen supply

  • compost bins have holes in walls to let oxygen enter

  • gardening forks are used to mix compost regularly so more oxygen passes to centre

  • mixing compost also breaks up large clumps and increases SA for decomposers to act on

The result of no oxygen in decomposition and its uses

• Decomposers will carry out anaerobic respiration

• This produces a mixture of gases including methane = “Biogas”

• Small-scale biogas generators are used to provide fuel for homes

  • these often use plant materials from food waste or animal manure

V10 - Decomposition

Decay in milk and why the practical mimicked decay

• bacteria in milk start decay process after being left at room temp for days

• bacteria use enzymes to produce acidic molecules which is why sour milk tastes acidic

• decay is a very slow process so the practical will model decay by using lipase enzyme

  • results aren’t strictly decay but will be approximately the same as decay

RP10: Decay

1. In a labelled “lipase” test tube, use pipette to place 5cm³ of lipase solution inside.

2. In a labelled “milk” test tube, add 5 drops of Cresol red indicator, 5cm³ of milk and 7cm³ of sodium carbonate solution.

   • solution should be purple since sodium carbonate solution is alkaline and cresol red is purple in alkaline conditions

3. Place a thermometer into milk test tube, and put both tubes into a beaker of water at our 1st chosen temp. Start with 20C, around room temp.

4. Wait for our solution temps to be the same as the beaker water.

5. Use a pipette to transfer 1cm³ of lipase solution to the test tube containing milk and stir. At the same time start a timer.

6. Lipase will start to break down fat molecules in the milk, which releases fatty acids and causes the milk solution to become acidic.

   • in acidic conditions, the indicator changes to yellow

7. Once solution is yellow, stop timing and records the results.

8. Repeat at a range of diff temps

RP10: Decay Variables

• independent - temp

• dependent - time taken for milk solution to be yellow

• control - volumes of solutions

RP10: Decay - key things to remember

• use clean test tube for milk solution for each experiment

  • any traces of lipase from previous experiments will trigger the reaction before we are ready

• since we are looking for colour change, it can be hard to decide when to stop timing

  • reduce effect of this by sharing data with other groups and calculating a mean

RP10: Decay - graph and results

• low temp = slow reaction, since enzymes work slowly at low temp

• at certain temp = reaction is taking place at fastest rate = optimum temp

• conditions that are warmer than optimum temp = reaction slows down, may stop completely since enzymes denature at higher temps

Results:

• Decay: decomposing microorganisms work faster in warm conditions but not in hot conditions, since enzymes denature when temp is too high

v11 - RP10: Decay

How abiotic factor changes can affect species distribution:

• the variation type shown through diff fox species

• the abiotic factor involved

Temperature showing geographic variation:

• North Africa desert fox - adapted to hot desert conditions

  • large ears increase SA so it loses heat more easily

  • not found in Europe where conditions are cooler

• Europe red fox - adapted to cooler conditions

  • further north, red fox disappears

• Arctic’s arctic fox - adapted to extremely cold conditions around Arctic Circle

  • very small ears reduce SA so less heat is lost to air

How abiotic factor changes can affect species distribution:

• the variation type shown through diff plant species

• the abiotic factor involved

Availability of water showing geographic variation:

• Cacti found in American desert - adapted to live where water is scarce

• Don’t find cacti in regions where water is more plentiful - find plants adapted to wetter conditions like ferns

How abiotic factor changes can affect species distribution:

• the variation type shown through wildebeest, bird (swallows), bats migration

• the abiotic factor involved

Rainfall patterns showing seasonal variation:

• Yearly huge wildebeest numbers migrate across Africa - following rainfall patterns in search of better grazing land

Summer and winter conditions showing seasonal variation:

• Swallows (bird type) breed in the UK summer and migrate to Africa’s warm conditions during winter

• Millions of bats migrate south from the US, to Mexico in the winter where conditions are warmer

Abiotic factors influenced by human activity, that change species distribution

Gases in the atmosphere:

• Lichen grows on rocks or trees

• They’re very sensitive to sulfur dioxide gas which can be produced by burning fossil fuels

• We find larger numbers of lichens where air is unpolluted

Levels of gases dissolved in water:

• if sewage is allowed into steams, this can cause dissolved oxygen levels to drop

• organisms like mayfly nymphs can’t live in low oxygen conditions = populations of these species can fall

V12 - Environmental Change

Biodiversity

The variety of all the different species of organisms on earth

Biodiversity importance

• species depend on each other for food and shelter

• species help maintain the environment - decomposers breaking down dead organisms

High Biodiversity

• lots of different species = ecosystem is less dependent on 1 species

  • if population of one species falls, its less likely to affect the whole ecosystem

• therefore makes an ecosystem more stable

Humans effect on Biodiversity and why we do this

Negative effect - deforestation:

• tropical forests contain rich biodiversity

• large areas are being destroyed to provide land for:

  • rice fields

  • grazing cattle

  • land used for crops, which are then used to make biofuels

Due to the reduction in habitats, (for farms, airports etc) this reduces biodiversity.

v13 - Biodiversity

Why are earths resources used more than ever before in recent years and what does this lead to

• last hundred years, population of humans has increased massively

• average standard of living has increased

These produce more waste, leading to pollution

How waste leads to pollution of water

Sewage:

• we make a large amount of sewage (urine and faeces)

• some countries release this into nearby waterways

• UK sewage is treated before released - but sometimes untreated sewage is accidentally released into rivers/streams

Fertilisers:

• river and streams can be polluted by this from farms

Both fertilisers and untreated sewage can cause dissolved oxygen levels to fall, killing aquatic organisms

Toxic chemicals:

• released into rivers from factories - kills river animals

REDUCED BIODIVERSITY

How waste leads to pollution of air

Burning coal in Power stations:

• acidic gases - cause acid rain

• smoke - kill plants and animals

REDUCED BIODIVERSITY

How waste leads to pollution of land

Landfills:

• millions of tons of waste dumped in these - destroy plant and animal habitats

• toxic chemicals can leach out of landfills - pollute the soil

• toxic chemicals are dumped directly on the land - kill living organisms

REDUCED BIODIVERSITY

v14 - waste management

Peat bogs/lands def and conditions

• Contain large amounts of dead plant materials

• Their conditions make decay very slow so they contain a lot of trapped carbon

Peat bog uses and the issues of uses

• These habitats are being destroyed = reduces the area of this habitat

  • This reduces the variety of animals, plants and microorganisms that live there = reducing biodiversity

• Once peat is extracted and used for cheap compost in farms, it begins to decay

  • releases a lot of CO2

• Some countries burn peat for energy (electricity)

  • releases CO2, contributing to climate change

Issues with alternatives of peat bog compost

• more expensive

• peat-free compost may increase the price of food

v15 - land use

Global warming and unnatural GW explanation

• Last hundred years, earths average temp is increasing

• It’s changed many times in the past from natural changes in the climate, but scientists believe the current increase is caused by human activities

Gases in global warming

• Many decades humans have released huge CO2 amounts into atmosphere

  • mainly due to burning fossil fuels

• Methane levels also increased

  • produced by bacteria in paddy fields, used to grow rice

  • released by cows passing gas

• Both are greenhouse gases = they trap heat in atmosphere = leading to GW

Peer review and the media on GW

• Thousand scientific papers have been published on GW

• These have been checked by other scientists before publishing (peer review)

• Peer review detects false claims and checks research validity

• Popular media reports (newspapers) aren’t subject to peer review = GW reports can be oversimplified, inaccurate or biased

How GW (global warming) affects animals and plants

Loss of habitats:

• reduction in arctic ice levels = population of arctic organisms (polar bears) fall since habitat is smaller

Birds/insects may extend their range north to cooler conditions

• many mosquito species carry diseases that affect humans (malaria)

• currently can’t survive UK cold

• GW - malaria insect range may spread to UK

Other:

• animal migration patterns of many may change

• spring plants in UK flower earlier due to warmth

Growing crops:

• in future may grow crops like grapes in the UK (where we can’t today)

• other parts of the world it may be too hot to grow necessary crops

v16 - Global warming

Reducing negative effects of humans on biodiversity

• Breeding programmes for many endangered species

• Protection and regeneration of rare habitats

• Field margins and hedgerows on farmer fields

• Governments less deforestation/co2

• Individuals recycling

Reducing negative effects of humans on biodiversity

• Breeding programmes for many endangered species

• increase Sumatran tiger numbers by zoos lead them to other zoos hoping they’ll breed

Reducing negative effects of humans on biodiversity

• Protection and regeneration of rare habitats

• Wetlands have high biodiversity - many are drained to grow crops - being protected or reflooded

Reducing negative effects of humans on biodiversity

• Field margins and hedgerows on farmer fields

• biodiversity is low since 1 crop is used for a huge field = no variety in species

• field margins - strips of land around fields so wild animals/plants can live

• hedgerows planted between fields since many diff plant/animal species live in them

• both preserve biodiversity on farms

Reducing negative effects of humans on biodiversity

• Governments

• Brazilian gov established national parks to protect the Amazon

• Govs reduce CO2 emissions by using renewable energy - UK electricity is a large % from windfarms

• reducing deforestation and co2 emissions can reduce loss of biodiversity

Reducing negative effects of humans on biodiversity

• Individuals

• recycling waste materials - lots are dumped in landfills which destroy habitats

• recycling means less waste is in landfills = less habitats are destroyed

• positive effect on biodiversity

v17 - maintaining biodiversity

Trophic levels

Positions on a food chain:

1. Level 1 are producers

2. Primary consumers

3. Secondary consumers

4. Tertiary consumers

Apex predator

Carnivores with no predators - aren’t killed and eaten by other animals.

What decomposers carry out and how?

• Break down dead plants, animals and waste products like faeces

  • by this, they return mineral ions back to the soil

• Carry this out by secreting (release) enzymes into the environment

• Enzymes digest dead materials

• Small soluble food molecules then diffuse back into the decomposer

v18 - trophic levels

Biomass

• A measure of the total mass of living material in each trophic level.

• It’s the living tissue of an organism, including proteins, lipids and carbs.

Calculating biomass of caterpillars in a food chain

• collect all caterpillars in an area and kill them

• dry them and weigh them = dry biomass

Is dry or wet biomass more useful

• dry - moisture content of organisms can vary widely and produce inaccurate results

How to avoid killing animals for biomass

• look up data needed in scientific journals

Pyramid of biomass def, example using the given food chain and explanation of levels

Represents trophic levels of a food chain. Biomass amount decreases for each level.

• Level 1 - Producer (tree)

• Level 2 - Primary consumer (caterpillar)

• Level 3 - Secondary consumer (small bird)

• Level 4 - Tertiary consumer (bird of prey)

Realistic pyramid shows that only 10% of biomass at one level passes to the next, so the number of organisms at each level decreases. Theres very few food chains with a large number of different trophic levels.

Why biomass amount decreases for each trophic level

• not all material ingested by bird is absorbed, some is egested as faeces

• some biomass absorbed is converted into waste products of metabolism and is released (e.g humans urea)

• large amount of biomass is used by the bird for respiration to release energy

  • energy is important for movement, and in the case of mammals and birds, maintaining constant body temp

• some is used for producing waste compounds from respiration (CO2 or H2O)

How much light energy is used by producers

1% that falls on producers is actually absorbed and used for photosynthesis

Efficiency of biomass transfer eq.

efficiency = gain in biomass/total biomass intake = d.p or x 100 for %

v19 - pyramids of biomass

Food security

Having enough food to feed a population

• very important as more live in cities and less grow their own food

• as pop increases we must find sustainable methods to feed everyone

6 biological threats to food security

• Birth rate is increasing

• Changing tastes

• New pests/pathogens

• Environmental change

• Resources

• Conflicts

biological threats to food security - Birth rate explained

Birth rate is increasing - pop growth means the food available will have to increase to feed everyone