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Abiotic factors (non-living): temp, pH, humidity etc

Biotic factors (living): competition, predation, mating

Definitions:

Habitat: Place where an organism lives e.g. field

Population: All of the organisms of one species in a habitat living together at the same time.

Community: Populations of different species in a habitat living at the same time.

Ecosystem: A community plus all the non-living factors (abiotic) in the area in which it resides.

Niche: The role of an organism within its habitat (where it goes/what it eats).

Species: Individuals with similar characteristics which can breed successfully to produce fertile offspring.

Importance of biotic & abiotic factors:

Abiotic factors such as temperature, light intensity and pH can affect enzyme activity, which in turn can affect how quickly photosynthesis takes place. The rate of photosynthesis is also affected by CO2 levels. Wind strength can affect how quickly evaporation of water takes place as well as transpiration (movement of water through a plant)

Biotic factors such as food availability can affect how many individuals of a species there are. The more food, the more reproduction. The amount of predators present can change numbers of individuals of species, as can competition for resources.

Pyramids of biomass: Less biomass at each level as there are fewer individuals of each species, despite each level individual having more mass on average.

Apex Predator

Primary consumers

2*C

3*C

Respiration

Decomposition

Producers

Energy loss to the left (decomposition):

All of the organisms in this pyramid of biomass eventually die and are broken down by microorganisms (known as saprobionts and detritivores) which use enzymes to do this. This then respire and release the carbon from the organisms as CO2 into the atmosphere to be taken up by plants. This is why a compost heap gets hot, as the decaying plant matter releases heat from the respiration of the decomposers. They therefore play a crucial role in ecosystem recycling and maintenance, as well as the carbon cycle.

Pyramid explained:

Producers are at the first trophic level, or the bottom of the food chain. They photosynthesise using light energy from the sun and turn it into sugars, which acts as a source of food for the primary consumer.

Primary consumers are typically a small herbivore or an insect, and by eating plants and growing in number, they act as a food source for secondary consumers

Secondary consumers (and tertiary subsequently) are larger carnivores and feed on the primary (& secondary) consumers. Since they feed on the small animals, they cannot digest the bone/teeth/fur and so less energy is available to them as the next stage in the pyramid.

Apex predators are not hunted or preyed upon by other organisms in their environment. There are very few of these individuals, so the amount of energy and biomass at this trophic level is less than levels preceding it.

Energy loss to the left (Respiration):

All of the organisms in this pyramid of biomass respire by using oxygen and glucose to release chemical energy in the form of ATP. This is how energy is lost from each stage and why there is less energy available to each level at the pyramid.

Adaptations for animals: Organisms living in different environments must be adapted to survive in different ways. Here we will discuss some examples of different environmental adaptations.

Climate is cold and windy (such as a polar climate):

  • Small surface area to volume ratio to reduce heat loss (polar bear, small ears, round body).

  • Layer of insulation (fat/fur such as those in elephant seals/polar bear)

  • Claws to grip ice

  • Waterproofing of any kind (polar bear hairs are hollow and waterproof)
     

Climate is hot and arid/dry, such as a desert:

  • Large surface area to volume ratio to maximise heat loss (elephant large ears).

  • Kidney/nephron adaptations so that very little urine produced (uric acid crystals excreted) nephron shorter

  • Active outside of hot times of the day.

Extremophiles are organisms that live in incredibly unfavourable conditions (abiotically speaking in general) such as microorganisms living in extreme pH, temperature or pressure.

Plant adaptations for dry/aquatic climates:

Dry:
Depressed stomata and curled leaves create microclimates reducing the water potential gradient. Less water lost by evaporation through transpiration. Waxy cuticle. Store of water such as those in a cactus.

Aquatic: Air sacs for buoyancy aid in plants such as in lilies or seaweed. Stomata are few in number and only on upper surface of plant.

Human impact on the environment:

Deforestation:
Removing trees and burning them for fuel releases CO2 from the combustion, and it means there are less trees to absorb carbon dioxide from the atmosphere by photosynthesis. They also destroy the habitats of animals and therefore kill certain individuals of species.

Pollution: Emissions of NO2 and SO2 dissolve into clouds to form acid rain (nitric and sulphuric acid) which pollute streams and lakes by lowering their pH (affecting most enzymes). Combustion of fossil fuels releases CO2 which contributes to the greenhouse effect by acting as a greenhouse gas.

Agriculture: Growing monoculture crops reduces biodiversity, whilst nitrate-rich fertilisers leak into the soil and into streams and rivers, where they cause eutrophication.

Fishing: Fishing trawlers destroy the ocean floor, removing photosynthetic seaweeds, as well as killing many species as bycatch. A huge reduction in aquatic biodiversity.

Random sampling:
-Grid out an area of habitat e.g. field/woodland and map out the grid into a series of coordinates.
-Use a random number generator to generate sets of coordinates.
-Place quadrat at coordinate corner and measure number of individuals or percentage cover of quadrat.
-Use a large sample size (number of samples) to make results more representative, as well as calculate a mean.
-Repeat the process multiple times, reducing the likelihood of the results arising due to chance.
-Number of individuals for the whole area/habitat calculated by multiplying quadrat mean with size of the area.

Global Warming

UV from sun

IR reflected

Atmosphere

Earth surface

The sun emits UV radiation, which passes through the atmosphere and heats up the earth. The earth gives off infrared radiation, which gets reflected back upon itself by the atmosphere. The amount of infrared radiation reflected can vary depending on the amount of greenhouse gases present. 

Carbon dioxide, water vapour and methane gas are all examples of greenhouse gases which reflect more heat back onto the earth.

As a result, the temperature on the earths surface rises, melting ice caps and causing sea levels to rise, as well as climate change. This phenomenon is known as global warming.

Distribution along a line:
-Taking samples using quadrats along a tape measure is known as a belt transect
-The disadvantage of this is that some areas are not sampled (missed).

Why this technique?
This belt transect technique is useful to see how distribution changes along a certain terrain e.g. measuring the distribution of plants towards shore from a beach, measuring abundance.

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