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This presentation was prepared for my Grade 11 Students. (this is not the final version). It covered some aspects of section E of 2004 Syllabus content.
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ECOLOGY
4 P R E P A R E D B Y : M U H A M A D N A B E E L U D D I N
Biology
Ecology
It is the scientific study of ecosystems
Can you define the following words?
Species
Habitat
Population
Community
Ecosystem : it is a biological community of interacting organisms and their physical environment.
Biosphere is the global sum of all ecosystems.
Ecosystem
Is made up of two components
A. Biotic factors: all the living organisms
Abiotic factors: The physical or non-living part of the ecosystem. Examples of abiotic factors includes:
• Water
• Sunlight
• Soil: structure
• Humidity/moisture
• Atmospheric gases
• Pressure and sound (for marine habitats)
• Can you add to this list?
Abiotic factor- Light
Photosynthesis
Light intensity affects photosynthesis rate
Plants living on forest floor prefer shade, other prefer greater light intensity
Abiotic factors-light
Length of day/night affects flowering and fruiting of plants in seasonal regions of Earth
Abiotic Factors-soil
Importance of Soil Anchorage
Provision of nutrients/minerals
Provision of water
Air to plants and soil organisms
Soil Formation-Weathering of rocks
There are three main methods
Physical: e.g. action of water waves
Chemical: e.g. acid rain
Biological : action of microorganisms or plant roots
Components of soil
Four components of soil
Mineral matter
Organic matter
Water content
Air content
How will the above affect plants and animal lives?
Types of Soil
Clay Loam Sand
Lots of clay, little sand and
little humus
1/2 sand, 1/3 clay and 1/6
load
Lots of sand, little clay and
humus
Many small clay particles Mixture of large and small
particles
Many large particles of sand
Water drains poorly (high
retentivity)
Water drains well Water drains too easily (low
retentivity) so soil is dry
Small air spaces, little air Intermediate size air space Large air space
Heavy to dig Intermediate Light and easy to dig
Can be waterlogged easily Intermediate Minerals are leached out of
soil more quickly
High water holding capacity Intermediate Low water holding capacity
Biotic Factors
Symbiosis- Revision
Symbiosis: is a close and often long-term interaction between two or more different biological species
Three main types:
Mutualism
Commensalism
Parasitism
Mutualism
Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits.
Explain how the organisms benefit from each other
Mutualism
Mutualism: Clown fish and Sea anemones
Sea anemones capture their prey by paralyzing them with discharged cnidoblasts. But Clownfish are not affected
Suggest what the sea anemone gains from this relationship
Image source: http://facstaff.cbu.edu/~seisen/ExamplesOfMutualism.htm
Mutualism in leguminous Plants
Commensalism
In ecology, commensalism is a class of relationship between two organisms where one organism benefits without affecting the other.
Commensalism: leopard shark and remora
Parasitism
Parasitism is a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.
Ecological Study Techniques
A sample study is done , i.e. a small portion of an area is studied
Why?
It is impossible to count all the number of plants of animals in an area
Precausion
Avoid degrading the habitat/environment
Avoid removing organism from their natural habitat
Ecological Study Techniques
1. Quadrats It is a square metal or wood frame of known area
It is used to estimate the number of species in an ecosystem
E.g. to estimate # of weeds in an area
A sample area is studied, then, the information is used to estimate the number of species in the entire area
E.g. 1m2 Quadrats are thrown 10 times at random in a 300 m2
area. The average per throw is calculated. That number is then multiplied by 300 to estimate the total number in the area
Example showing how the number of weeds in an area can be estimated
Total # =90
Average per throw = 90/10 =9 (density)
Estimated number in 300 m2 = 9 * 300
=2700 species
Quadrat
(Throws)
1 2 3 4 5 6 7 8 9 10
Organisms 10 5 6 7 10 11 10 13 8 10
Quadrats
Square quadrat framefor determining
population densities
Subdivided quadrat frame
for determining % cover of species
Quadrat frames, constructed from wood or metal, are used to investigate the distribution
of species
Ecological study using Quadrat
http://4.bp.blogspot.com/-xSCznJPd_ak/TckwoD5nAQI/AAAAAAAAAIw/24m4xT5wYi0/s1600/quadrat.jpg
Ecological Study Technique
2. Nets Nets are used for sampling small moving animals such as insects.
They can also be used to estimate the number of species in pond.
http://wiki.bugwood.org/uploads/Fig27_bugnet.jpg
Nets
Using sweep nets for ecological studies
Ecological Study Technique
3. Transects Line transects are used in habitats where there is a clear change in
conditions and the distribution of the vegetation or sessile (immobile) animal from one point to another.
E.g. of area that can be studied : river banks and swampy areas
A line transect is one in which all individual organisms touching the tape/string are recorded
Ecological Study Technique
Jars/bottles and pitfall traps Bottles can be used to set pitfall traps, so that they cannot escape
easily
Jars/bottles can be used to study aquatic organisms, e.g. a person may collect a few sample of water from a stream, river, trench, then take the sample to a lab, and then identify microorganism using a microscope, or by culture technique (using agar plates)
Line Transect
http://teacheratsea.wordpress.com/2013/07/31/julia-harvey-determining-population-sizea-day-in-my-life-cruising-july-27-2013/
Pitfall trap
http://www.bbc.co.uk/bitesize/standard/biology/biosphere/investigating_an_ecosystem/revision/3/
Transects
Belt transect involves laying a tape through the area of study and sampling the population with Quadrats positioned at regular intervals alongside the tape
Species Frequency
The percentage frequency of a species is the percentage of sample units (usually Quadrats) in which the species occurs.
E.g. If a species X occurs in 10 out of 25 Quadrats thrown randomly, what is its frequency?
Solution: = 10/25 * 100 = 40 %
Density
Density of a population is the number of organisms in 1m2 found using a quadrat of sides 1m.
Average number of organisms inside the quadrat on ten throws is the density.
Check slide 22
ANY QUESTIONS?
Lab # 20
Aim:
Introduction