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