6.3.1 Ecosystems and Populations

Niche definition

 The Role of an organism in the ecosystem

Ecosystem definition

all the organisms living in a certain area and all the abiotic and biotic factors

Why can 2 species with identical niches never coexist?

Competing for food and shelter → one species goes extinct

Examples of biotic factors

Competition

Predation

parasitism

Examples of abiotic factors

Temperature

Light intensity

Oxygen concentration

pH

Which abiotic factors are lethal at both extremes

pH and temperature

Which abiotic factor is lethal at one extreme

O₂ concentration

pollutants

why are ecosystems dynamic ?

they are constantly changing

what are the two types of changes in a ecosystem

Cyclic changes

Directional changes

Examples of cyclic and directional changes

Cyclic → Tide, seasonal light fluctuations

Directional → Fires and earthquake ( Erratic)

what does a food chain show

Flow of energy from producer to consumer

Examples of decomposers

Bacteria

Fungi

Explain why a low % of sunlight is converted to chemical energy by plant

Light is reflected

not all light used in photosynthesis ( photolysis)

transmission of light

How to work out Net primary productivity ( NPP)

Net = Gross productivity - Respiration

Why do mammals have a greater energy loss?

Use energy to maintain our own body temperature through metabolic reactions

Why is ecological efficiency never 100%

Energy is lost as heat ( respiration )

cant digest cellulose

not all of plant is eaten

ways to increase Net primary productivity

Increase light levels

Increase water availability

Remove competition

pest control

what is biomass

dry mass of living material

what is energy stored as in producers

Biomass

what is a producer

photoautotrophs

what are the different consumers?

primary → eats producer

secondary → eats primary

what is meant by gross productivity ?

Available energy in organism

what is meant by net productivity

amount of energy available to the next trophic level

Ways to increase secondary productivity ( agriculture ecological efficiency)

use anabolic steroids

selectivity breed

harvest before adulthood

equipment used to measure energy content / Biomass of an organism

limitations

Calorimeter

Limitations → Heat loss, incomplete combustion values are a underestimate true value

Method to Measure energy content / biomass of an organism

Collect sample

kill organism

Oven at 80°C ( evaporate all water / too high organic material decays) until constant mass

how to work out efficiency of biomass transfer between trophic levels ?

transfer of energy (Image)

Why is consumer to consumer efficiency of energy higher then producer to consumer

Plants have more indigestible material ( cellulose) then animals

How to increase accuracy of measuring biomass of organism method

Include all individual organism at each tropic level

how to increase Net primary productivity ( agriculture)

Herbicides → kills weed that compete with crops

Insecticides → kills insect pests that damage crops

Natural predator → eat pest species ( less biomass is lost)

Disadvantages of agriculture ways to increase NPP and NSP

unethical ( limiting movement)

What are the processed involved in the carbon cycle

Photosynthesis

Decomposition

Respiration

Combustion

Release from volcanoes

weathering

Photosynthesis role in carbon cycle ?

Carbon (CO₂) absorbed by plants used to make organic molecules

Carbon is passed to primary consumer when plant is eaten then continually passed on.

Respiration role in Carbon cycle ?

Carbon is returned to the air when all living organisms respire as CO₂

Decomposition role in Carbon cycle ?

Decomposers Secrete enzymes which break down carbon compounds in dead organic material

reabsorb the products and use in respiration.

What are detritivores ?

feed on dead organic matter which increases SA: Vol ratio → increases rate of decomposition

differences between Detritivores and Decomposers ( Saprotrophs)

Detritivores → Internal digestion, increase SA: Vol ratio

Decomposers → external digestion, secrete enzymes

Role of Combustion in carbon cycle?

In Dead organic matter, carbon compounds are turned into fossil fuels (heat and pressure)

carbon in fossil fuels is released when combusted

what is saprobiontic nutrition

Feeding on dead organic matter

what are the units of biomass for ocean organisms

gm⁻³ ( yr⁻¹)

what are the units for biomass for land organisms

gm⁻² ( yr⁻¹)

What are the main processes in the nitrogen cycle

nitrification

ammonification

denitrification

nitrogen fixation.

Carbon cycle (Image)

why is nitrogen important in plants and animals

needed to make nucleic acids and proteins for growth

what are the Bacteria involved in nitrification

Nitrosomonas

Nitrobacter

what happens in nitrification

NH₄⁺ converted into nitrates that are used by plant

Nitrification (image)

(nitrification) what are the functions of the bacteria involved

Nitrosomonas → converts NH₄⁺ → NO₂⁻

Nitrobacter → converts NO₂⁻ → NO₃⁻

what happens in ammonification

Nitrates decomposed into ammonia / ammonium ions by decomposers

ammonification (Image)

what happens in denitrification

Nitrates are converted into Nitrogen gas in anaerobic conditions ( waterlogged soil)

Denitrification (Image)

what are the bacteria involved in nitrogen fixation

Azotobacter

Rhizobium

what happens in nitrogen fixation

nitrogen gas is converted into ammonia by bacteria

NH₃ used by plant

Nitrogen fixation (Image)

what is the relationship between Rhizobium and the plant

Mutualistic relationship

plant receives Nitrogen compounds from Rhizobium

Rhizobium receives carbohydrates from plant

where are Rhizobium found?

inside root nodule of leguminous plants ( peas, beans and clovers)

which processes in the nitrogen cycle products are used by plants

nitrification

ammonification

nitrogen fixation

what happens to the products in denitrification (Nitrogen cycle)

N₂ goes to the atmosphere

Nitrogen cycle ( Image)

What is the bacteria involved in Denitrification

Pseudomonas

what is meant by the term succession ?

Gradual directional change in a community of organisms over time

what are the types of succession ?

Primary succession

Secondary succession

succession effect on environmental conditions ?

biotic conditions change as abiotic conditions change

makes more conditions more suitable for other species

where does primary succession occur

Original area has no soil or living organisms present

what are pioneer species ?

First species to colonise an area

How are seeds and spores transported to new land?

Blown by the wind

Function of pioneering species

Help to stabilise an environment making it possible for other species to grow there → by changing abiotic and biotic conditions

Why are pioneering species involved in primary succession

They are specialised to survive in harsh conditions

What are the conditions of the new land in the pioneer stage of succession

Low water availability → no soil to retain water

low minerals / nutrients → no soil

fluctuating temperature → directly exposed to sun

example of a pioneering species

Marram grass can grow on sand dunes → deep roots to get water.

What is meant by climax community ?

when the ecosystem supports the largest and most complex community of organisms it can

which species change the abiotic environment the most ?

The dominant species in the ecosystem

What happens at each stage of primary succession

pioneering species changes conditions → no longer best adapted species

better adapted plants / animals for the new conditions move in → out compete the old organisms → dominant species in ecosystem

what is meant by climatic climax ?

climax community for a particular climate

What is Secondary succession ?

succession that happens on land that has been cleared of all plants but has soil.

Examples of conditions for secondary succession

After a forest fire

forest cut down by humans

difference between primary and secondary succession ?

Primary → No soil / organic material

Secondary → has soil/ starts at a later stage / pioneering species are larger plants

Humans effect on succession ?

Deflected successions

what is meant by Plagioclimax

A deflected climax community

what is meant by deflected succession ?

the path of succession has been altered from its natural course.

Ways of humans preventing Succession

Clearing deciduous woodlands for agriculture/ settlement

mowing

livestock used for grazing

Stages of succession ( Process)

Pioneer community → spores / seeds are blown by wind to bare rock → pioneer species are adapted to harsh conditions

Intermediate community → Herb species / shrubs and trees

Climax community → community is stable and dominated by few trees / organisms

Pioneer species die → decomposed → increases organic / water content of soil

Advantages of a plagioclimax

prevents natural succession → stops land from being replaced by climax community → cannot support the same species → decrease species diversity.

Best sampling technique to use to measure succession

Transect

How to use a line transect to measure succession

Record what is touching the tape

How to use belt transect to measure succession?

Quadrat is placed alongside the tape

what are the types of belt transects ?

continuous → Record along the whole length of tape

Interrupted → Record at intervals along the tape

equation to work out population size

Disadvantages of using a point quadrat

very small or rare species may be missed

Compare the 3 types of transects ?

Line transect → quick and easier to carry out

Belt transect → provide more data

Interrupted transect → quicker then belt but gives more information then line

definition of population ?

The number of organisms of the same species in a habitat

what is meant by population limiting factors

Factors that prevent the population from increasing

What are the two types of limiting factors ?

Abiotic

Biotic

what is meant by carrying capacity

Maximum population size of a species that an ecosystem can support

Intraspecific competition graph

describe the changes

1) resources are in excess so Hare population increases as they can survive and reproduce

2) Resources become limiting as population is too large → population decreases

3) small population of hares → less competition so population starts to increase

4) Carrying capacity of the ecosystem

what regulates the predation population relationship

Negative feedback

what is meant by negative feedback

A system change in way to return to a stable state

Predation competition graph

describe the changes

1) Lynx population increases after hare population increases → more food available for lynx

2) lynx eat more hares so the population decreases

3) Reduced hare population means there less food for lynx so there population decreases