Biology

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  • Created by: Charlotte
  • Created on: 22-11-12 12:10

Estimating Population Sizes!

POPULATION: All the organisms of one species in a habitat.
COMMUNITY:
Populations of different species in a habitat make a community. 

QUADRAT
You can estimate polpulation sizes by using a QUADRAT (a square divided into smaller sections)

Quadrat (http://www.bbc.co.uk/schools/gcsebitesize/science/images/bio_quadrat_alt.jpg) 

You can count the amount of living organisms found in one quadrat's area (squared) and times it by the total area (e.g a field) in metres squared! 

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Estimating Population Sizes! (2)

CAPTURE - RECAPTURE

1) Capture a sample of the population and mark the animals in a harmless way (marker pen)

2) Release them back into the environment

3) Recapture another sample of the population. Count how many of this sample are marked.

4) Estimate the population size using this equation:

Population Size = Number in first sample X number in second sample 
Number in second sample previously marked 

Sample Size affects the accuracy of the estimate, the bigger the sample, the more accurate your estimate of the total population!

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Estimating Population Sizes! (3)

About these methods... QUADRAT and CAPTURE-RECAPTURE
1) Sample size affects accuracy of your estimate
2) Using Capture-Recapture data you have to assume:

  • There's no changes in the populationsize due to deaths, Immigration or Emigration!
  • The sampling methods for the capturing were identical (Pitfall trap the same each time)
  • The marking method didnt affect the organisms chance of survival (by being visible to predators)

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/bugtrap2.gif) A Pitfall Trap (made using a small pot level with the soil, with a cover that leaves enough gap for creature to enter the trap.) 

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Ecosystems and Distribution of Organisms

Term Description
Environment:  All the conditions that surround a living organism

Habitat: The place where an organism lives

Population:  All the members of a single species that live in a habitat

Community: All the populations of different organisms that live together in a habitat

Ecosystem:  A community and the habitat in which it lives

Ecosystems are self supporting

  • They cantain almost eveything they need to support themselves. Water, nutrients and essential elements like Carbon- they all get recycled in an ecosystem.
  • The only thing they need from outside is an energy source. THE SUN! 
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Transects and Kite Diagrams

TRANSECTS: Are used to investigate the Distribution of Organisms

Using a Transect:

  • Measure out a line using a tape measure over a particular area you want to study.
  • Place Quadrats all the way along the line, count and record the different organisms you find in each quadrat.
  • If its difficult to estimate the amount of each organism (the amount of blades of grass- bit tricky) use Percentage Cover (%) estimating the percentage of the quadrat area that is covered by the organism. (so if a quadrat lies on a field of grass its most likely going to be 100% area of grass)
  • You can plot the results of your findings on a KITE DIAGRAM!
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Kite Diagrams

KITE DIAGRAMS: A way of representing a transects data!
The Kite diagram below shows the distribution and abundance (number) of organisms along the length of the transect

The X-axis shows the distance alond the transect line! The thickness of the kite shows the abundance of organisms.

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Zonation

The Distribution Of Organisms Is Affected By Abiotic Factors

Abiotic Factors = are the non-living, physical factors of an environment e.g. light, temoerature, water, oxygen, salinity (salt level) and soil quality.

  • Organisms are adapted to live in certain physical conditions. This means theyre more likely to survive and reproduce in areas with these conditions. E.g. Woodland ferns are adapted to living in shade, so you dont often find them living in sunny, open areas.
  • Many organisms can only survive in the conditions they're adapted to.

Changes in Abiotic factors can lead to Zonation

ZONATION IS THE GRADUAL CHANGE IN THE DISTRIBUTION OF SPECIES ACROSS A HABITAT

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Zonation

(http://www.cbd.int/programmes/areas/water/toolkit/images/chpt6/Figure%207.3.3_Zonation_BT.jpg)

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Biodiversity

Biodiversity is a Measure of the Variety of Life in an Area

1) The amount of Variation Between Individuals of the same species in an area.
2) The number of Different Species in an area.
3) the number of Different Habitats in an area. 

Biodiverty is important - ecosystems with a high level of biodiversity are healthier than those without a high level, more diverse environments can cope easier with changes.

Native Woodlands Plantations

Variety of tree species- e.g birch, ok. One species of tree- (planted for timber)
Variety of plant species- e.g flowers, shrubs. Fewer plant species- (trees take up room0
Variety of habitats- e.g different shurbs, leaf litter. Fewer habitats-aren't enough plant types.
Variety of animal- species- birds, bugs etc Fewer animals- not many food sources.

Same with Fish farms and Natural lakes

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Photosynthesis!!

Photosynthesis uses energy from the sun to change carbon dioxide and water into glucose and oxygen.

 (http://www.brilliantbiologystudent.com/images/photosynthesis_symbol_equation.jpg)

Photosynthesis happens in TWO main stages:

1) Light energy is used to split water into oxygen gas and hydrogen ions.
2) Carbon dioxide gas them combines with hydrogen ions to make glucose and water.


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How is Glucose used?

Glucose is converted into other substances:

1. Respiration
Plants use some of the glucose for respiration, this releases energy enabling the plant to convert the rest of the glucose for other uses.
2. Making cell walls
Glucose is converted into cellulose for making cell walls.
3. Storage in seeds
Glucose is turned into LIPIDS (fats and oils) for storing in seeds. Sunflower seeds, for example contain a lot of oil. 
4. Storage as starch 
Glucose is turned into starch and stored in roots, stems and leaves. For use at night when photsynthesis stops. Starch is insoluble so good for storing as it can't move)
5. Making Proteins
Glucose is combined with nitrates to make amino acids, proteins, for growth and repair

 

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Limiting Factors

There are THREE LIMITING FACTORS that contol the RATE OF PHOTOSYNTHESIS!

LIGHT
1) If the Light level is raised, the rate of photsynthesis will increase but only to a certain point.

2) Beyond that it won't make any difference because then itll be the temperature or CO2 level which is now the limiting factor.

CARBON DIOXIDE
1) As with light intensity the amount of CO2 will only increase the rate of photosynthesis up to a point. After this the CO2 is no longer the limiting factor.

2) So as long as Light and CO2 is in plenty, temperature must be the limiting factor. 

TEMPERATURE
Photosynthesis works best when its warm but not too hot!
1) Temp increases, so does the rate of Photosynthesis- but if too hot.. enzymes will denature! so the rate rapidly decreases. (This happens at aorund 45C) 

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Diffusion

DIFFUSUION: is the NET MOVEMENT of PARTICLES from an AREA OF HIGH CONCENTRATION to an AREA OF LOW CONCENTRATION

(http://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Diffusion.svg/220px-Diffusion.svg.png)

DONT GET DIFFUSION AND OSMOSIS MIXED UP!

DIFFUSION DOESN'T HAVE A PARTIALLY PERMEABLE MEMBRANE INVOLVED. 

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Leaves

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/bi05004.gif)

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Leaf adaptations...

Adaptation  Purpose

Epidermis is thin and transparent
To allow more light to reach the Pallisade cells

Thin cuticle made of wax
Protect leaf without blocking light

Pallisade cell layer at top of leaf
To absorb more light

Spongy mesosphyll layer
Air spaces allow CO2 to diffuse through leaf and increases surface area.

Pallisade cells contain many Chloroplasts
To absorb all the available light!

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Plants Photosynthesise and Respire

Photosynthesis and respiration are opposite processes:

Photosynthesis: Carbon Dioxide + water --> Glucose + Water (Requires energy)

Respiration: Glucose + Oxygen --> Carbon Dioxide + Water (Energy Released)

Photosynthesis only happens in the DAY, but plants still need to respire in the NIGHT to live so they take in oxygen and do a reverse reaction to produce energy!

Plants exchange gases by diffusion:

Photosynthesis: Uses up a lot of CO2- so when its nearly all gone more diffuses through the stomata into the leaf from an area of high concentration (outside leaf) to an area of low concentration (inside leaf). 

Also lots of oxygen is being made and therefore moves from high ceoncentration (inside leaf) to an area of lower concentration (outside leaf). 

At night its the opposite way round.....

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Vascular Bundles

 An example of a Vascular Bundle.

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Photosynthetic pigments

Photosynthetic pigments - Higher tier

Plants use more than one photosynthetic pigment to absorb light. This maximises the use of energy from the Sun. These pigments include:

  • Chlorophyll a (wavelengths of 400-450nm and 600-650nm)
  • Chlorophyll b (wavelengths of 450-500nm and 600-650nm)
  • Xanthophyll (wavelengths 400-530nm)
  • Carotene (wavelengths 400-550nm)

Chlorophyll a is the main pigment. It absorbs light mainly in the red and blue regions of the spectrum.

Chlorophyll b, xanthophyll and carotene are 'accessory pigments'. They absorb light from other regions of the spectrum and pass the energy onto chlorophyll a.

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