ECOLOGY
EJC HONOURS DAY 2013
1
What is Ecology? 2
Greek for ‘study of house’
It is the scientific study of the relationship of living things to each other and the environment around them
“The first law of ecology is that everything is related to everything else” – Barry Commoner, American biologist, teacher an activist.
It is important to know and understand the various relationships. A simple example is given in the following story.
The sad story of Lake Victoria –
By Kassandra, age 11 3
Lake Victoria in in equatorial Africa is the
second largest lake in the world. It was full of
life with many species of fish, plants, trees and
other land animals. In 1858, the British found this
land and claimed it for themselves even though
there were already people living there. The
British started to make it a good environment for
themselves and cut down trees to make room for
crops like coffee, tea and banana trees.
The sad story of Lake Victoria (cont’d) 4
The British then looked to fishing for enjoyment. They
fished for the ngege and eventually led the species to
extinction. To replace the ngege the British introduced
the tilapia as well as the Nile Perch to Lake Victoria.
The British only added the Nile perch to make it fun
to fish. It was a huge fish which weighed up to 300
pounds. Anybody would love to catch a 300 pound
fish and have that much food afterwards. The Nile
perch was so big and it ate so much that it put most
of the other fish to extinction.
The sad story of Lake Victoria (cont’d) 5
But they ran into a problem. These fish were so big they wouldn’t dry without rotting. Instead of drying in the sun the Nile perch needed to be roasted over fire. They never thought about the ecosystem. Many trees around the lake were cut to provide wood for the fire. The trees had been holding the soil together. Taking the trees out caused erosion.
The lake ended up getting too many nutrients and the nutrient-rich water made it easy for algae to grow. When the algae died it sank to the bottom of the lake and rotted. The rotting algae used the oxygen in the lake which the fish need to breathe. Many species of fish died and became extinct.
The sad story of Lake Victoria (cont’d) 6
The water became polluted and carried many
human diseases in it. Many humans around the lake
had to suffer from the symptoms of the diseases.
So, think back to the beginning. The British only
meant to change one thing but ended up changing
almost everything. Once you take a part of an
ecosystem away it changes the whole thing.
Types of Ecosystems 7
Two main types of ecosystems
Aquatic (found in a body of water)
Marine
Freshwater
Terrestrial (found only on land)
Tundra
Taiga
Deciduous forest
Grassland.
FRESH WATER POND ECOSYSTEM 8
Characteristics of a Pond 9
A body of water which can be either natural or
man-made
Usually shallow, about 12-15 feet in depth, so
sunlight penetrates to the bottom
Plants either grow entirely underwater or partially
on the surface
Supports a large variety of animal and plant life
Characteristics of a Pond 10
Examples of animal and plant life include:
Birds
Crayfish
Small fish
Frogs
Insects
Turtles
Protozoa
Algae
Lily pads, etc.
Ecosystems 11
An ecosystem is formed from the cohabitation of
plants, animals, microorganisms and a surrounding
environment.
Any group of living and nonliving things interacting
with each other can be considered an ecosystem.
A pond ecosystem refers to a community of
freshwater organisms largely dependent on each of
the surviving species to maintain a life cycle.
Ecosystems 12
Within each ecosystem are habitats – the places where different populations live – which must supply the needs of organisms, such as food, water, temperature, oxygen and minerals.
In some ecosystems, a habitat is specific to a population, while in others, e.g. a small pond (or even an aquarium) several populations may co-exist
A community refers to the organisms (plants and animals) in an ecosystem and is formed when all of the populations interact.
Ecosystems 13
A biome is a major class of ecologically similar
communities of plants, animals and soil organisms, often
referred to as ecosystems.
In other words, biomes are ecosystems where several
habitats intersect. Biomes are defined based on factors
such as plant structures (such as trees, shrubs and
grasses) and are often identified with particular
patterns of ecological succession and climax vegetation.
The Earth itself is one large biome. Smaller biomes
include deserts, grasslands and rainforests.
Ecosystems – Example of a Biome 14
Ecosystems 15
Energy and water are vital to the survival of an
ecosystem and the preservation and restoration of an
ecosystem’s resources is called conservation.
When resources become limited, conservation becomes
more important, with an increased need for recycling.
If conservation efforts fail, then species become
endangered (not enough habitat to support all the
members of the population or too many members killed
in too short a time) and extinction can occur (habitat
vanishes and/or all members of a population die).
Ecosystems 16
Ecological succession
Observed process of change in the species structure of
a community over time.
May be initiated either by formation of new,
unoccupied habitat (e.g. landslide) or by some form of
disturbance (e.g. fire) to an existing community.
Climax Community
A community that has reached a steady state through
ecological succession.
Ecosystems 17
Eutrophication
An ecosystem’s response to the increase in its primary
productivity. E.g. increased level of nutrients may cause
the phytoplankton to increase and disrupt the normal
functioning of the ecosystem.
Habitats of a Pond Ecosystem 18
Shore
May be rocky (won’t allow plants to grow), sandy or
muddy (attract grasses, worms, insects and
microorganisms)
Surface Film – top 6 inches of water on pond’s
surface
Excellent breeding ground for mosquito larvae, water
striders, marsh traders, free-floating organisms and
organisms that can walk on the surface of water.
Habitats of a Pond Ecosystem 19
Open Water
Hosts the following:
Fish (feed on plankton)
Plankton (organisms that inhabit the water column of oceans,
seas, and bodies of fresh water and provide a crucial supply
of food to most aquatic life)
Phytoplankton (various types of algae) and
Zooplankton (insect larvae, rotifers, small crustaceans and
invertebrates) .
Habitats of a Pond Ecosystem 20
Bottom Water
Varies depending upon the pond's depth. Shallow ponds
with sandy bottoms provide a nesting environment for
earthworms, snails and insects. Deep-ended ponds have
muddy bottoms, which allow various microorganisms such
as flatworms, rat-tailed maggots and dragonfly nymphs
to reproduce and survive. These animals feed on dead
organic matter that makes its way to the bottom.
Food Chain of a Pond’s Ecosystem 21
Basic trophic levels (the position an organism occupies in
a food chain)
Level 1
Producers & Autotrophs e.g. phytoplanktons and plants
Prepare their own food through photosynthesis and using
nutrients in soil and water
They do not eat other living things
Level 2
Primary Consumers or Herbivores e.g. insects, crustaceans
Inhabit the pond and consume plants
Food Chain of a Pond’s Ecosystem 22
Level 3
Secondary consumers or Carnivores which feed on both the plants and herbivores atop the first and second trophic levels.
Level 4
Decomposers or saprotrophic organisms
Located on the bottom of the food chain
Help decompose dead plants and animals, as well as animal waste, and turn them into chemical nutrients which plants will take up through their roots.
Food Chain of a Pond’s Ecosystem 23
Level 4 (cont’d)
These nutrients supply the necessary life force for the
first trophic level organisms to produce food for the
second trophic organisms, etc. which results in the
perpetual flow of energy in the pond's ecosystem.
Factors of an Ecosystem 24
Non-biological (or abiotic) factors include sunlight, water, air and soil
Water – also an essential element to life
Air – provides oxygen, nitrogen, and carbon dioxide to living species and allows the dissemination of pollen and spores
Soil – a source of nutrition as well as physical support.
Temperature – should not exceed certain extremes, even if tolerance to heat is significant for some species
Light – provides energy to the ecosystem (e.g. through photosynthesis).
Factors of an Ecosystem 25
Biological (or biotic) factors include animals, humans
and plants
A balanced ecosystem is one in which the types and
number of organisms are consistently maintained.
Symbiosis is a close ecological relationship between
the individuals of two (or more) different species.
Relationships in an Ecosystem 26
A symbiotic relationship in which:
Both species benefit
Mutualism
One species benefits and the other is unaffected
Commensalism (e.g. bird living in a tree)
One species benefits and the other is harmed
Parasitism
Neither species benefits
Competition
Both species interact but neither is affected
Neutralism.
Relationships in an Ecosystem 27
Ecological Pyramid (also known as trophic pyramid or energy pyramid)
A graphical representation designed to show the biomass or biomass productivity at each trophic level in a given ecosystem. It begins with producers on the bottom and proceeds through the various trophic levels, the highest of which is on top.
Food chain
A diagram showing a linear relationship of the feeding connection between species in an ecological community. It begins with a species that eats no other species and ends with a species that is eaten by no other species (in that community).
Example of a Bird’s Ecosystem 28
Example of Terrestrial Ecosystem 29
IMPORTANT NOTE 30
One of the requirements for this honour asks you to
include ecological pyramids for a mammal, bird,
amphibian and reptile. Do not simply reproduce the
pyramid below:
IMPORTANT NOTE 31
At least ensure that you also give examples of
appropriate organisms which can be found at each
level in the pyramid for the animal you are
focussing on.
SOURCES 32
http://www.thewaterpage.com/pond-ecosystem.htm
http://en.wikibooks.org/wiki/Adventist_Youth_Hono
rs_Answer_Book/Nature/Ecology
http://eng.me.go.kr/content.do?method=moveCont
ent&menuCode=res_kid_eco_ecosystem
http://www.fi.edu/tfi/units/life/habitat/
SOURCES 33
http://wwf.panda.org/about_our_earth/teacher_r
esources/webfieldtrips/ecological_balance/eco_int
eract/
http://www.hubbardbrook.org/mirrorlake_kids_tou
r/what_is_ecology.htm
http://en.wikipedia.org/wiki/Pond
http://masho0oq.blogspot.com/2006/02/ecosyste
m.html