2.0 ECOLOGY

BY : MDM. NURFAZLINI ISMAIL

2.1 ECOSYSTEM CONCEPT

• Define ecosystem

• Describe lake ecosystem based on :

• Light penetration

• Distance from shore and water depth

• Describe terrestrial ecosystem of tropical rainforest stratification

ECOSYSTEM

• A community (biotic component) and the physical environment (abiotic component) that mutually interact and function together to form a stable and balanced natural system

• Biotic component :

• Autotroph/producer

• An organism that obtain organic molecules by synthesizing them from inorganic materials.

• Heterotroph/consumer

• Organisms that cannot synthesize their own food from inorganic materials and therefore must live either at the expense of autotroph, other heterotrophs, or upon decaying

• Biotic component :

• Detritivore

• An organism (such as an earthworm or crab) that consumes fragments of dead organisms

• Decomposer (saprophyte)

• A heterotroph that breaks down organics material and uses the decomposition products to supply it with energy. Decomposers are microorganisms of decay.

• Abiotic component:

• Non-living factors that interact with one another and with the biotic components to form a natural balanced system.

• The atmosphere is the gaseous envelope surrounding Earth

• The hydrosphere is Earth’s supply of water (liquid and frozen, fresh and salty)

• The lithosphere is the soil and rock of the Earth’s crust.

LAKE ECOSYSTEM

• Lakes are standing bodies of freshwater produced by geologic processes.

• Lake ecosystem can be discuss based on :

• Light penetration (photic & aphotic)

• Distance from shore and water depth

• Consist of 4 zones, defined by :

• Distance from shore

• Littoral zone

• Limnetic zone (pelagic zone)

• Water depth

• Profundal zone

• Benthic zone

Lake Ecosystem : Distance From Shore and Water Depth

Lake Ecosystem : Light Penetration

Photic zone

Light penetration

sufficient for

photosynthesis

Aphotic zone

Insufficient light for

photosynthesis.

Water below the

level of light

penetration / light

does not penetrate

Distance From Shore: Littoral Zone

• Shallow, well-lit waters close to shore

• Rooted & floating aquatic plants dominant with insects, small crustaceans, frogs & fish

• Diversity is greatest here

Littoral Limnetic

Distance From Shore: Limnetic Zone

•Well-lit, open surface water, farther from shore, extending to depth where photosynthesis is insignificant

•Occupied by phytoplankton, zooplankton, higher animals

•Produces food and oxygen that supports most of lake’s consumers

Littoral Limnetic

Water Depth: Profundal Zone

Littoral Limnetic

Profundal

• Consists of deep, aphotic regions

• Too dark for photosynthesis

• Oxygen levels are low

• Inhabited by fish adapted to cool dark waters

Water Depth: Benthic Zone

Littoral Limnetic

Profundal

• The sediments at the bottom soil

• Zone of decomposition where plants materials either decay or sink to the bottom and accumulates.

• Dominated by bacteria and fungi(benthos).

Benthic

Terrestrial Ecosystem: Tropical Rainforest Stratification• Structurally, the tropical rain forest is considered to have five strata;

emergent, canopy, understory, shrubs and a ground layer of herbaceous plants.

• The uppermost layer of very tall trees in the tropical rain forest is often discontinuous and the individual trees are referred to as emergents.

• Sunlight is a major factor contribute to the stratification

Understory

Canopy

Emergent

Shrubs

Forest floor

Adaptations Of Plants In Tropical Rainforest

1. Thin smooth barks

2. Lianas

3. Drip tips

4. Buttresses

5. Prop and stilt roots

6. Epiphytes

Adaptations Of Plants In Tropical Rainforest

• Buttress root

• Presence in many large trees that may help to transport water, increase the surface area for gaseous exchange or provide greater stability (to support heavy weight of tall trees)

Adaptations Of Plants In Tropical Rainforest

• Lianas that festoon the rainforest trees

• Climbing woody vines, have their roots in the ground and climb high into the tree canopy to reach available light

Adaptations Of Plants In Tropical Rainforest

• Most tree have thin smooth barks

• The smoothness of the barks makes it difficult for other plants to grow on their surface

• Most leaves look very similar and have a drip tip

• These drip tips enable raindrops to run off quickly

Adaptations Of Plants In Tropical Rainforest

• Epiphytes on the trunks and branches

• An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain or from debris accumulating around it

• Grow on trees to take advantage of the sunlight in the canopy

• Includes fern, orchids, mosses and lichens

Adaptations Of Plants In Tropical Rainforest

• Prop and stilt roots

• Help give support and are characteristics of tropical palms growing in shallow, wet soils

Strata Type of tree Animal of

community

Emergent Tualang tree Eagle

Canopy Nephelium sp. Beetle

understory Hibiscus rosasinensis Honey bee

Shrub / Dryopteris (fern) Reptile

Ground layer Bryophyta Ant

2.2 BIOGEOCHEMICAL CYCLE

• Illustrate phosphorus Cycle

• Summarize the movements of phosphorus between living and non living components of the biosphere.

• Living organisms require phosphorus as it is a key component of molecule that store energy, such as ATP, DNA and phospholipid.

• Phosphorus is available in the form of inorganic phosphate ion (PO4ˉ³)

• The reservoir for phosphorus are in sedimentary rocks of marine, soil, ocean and organisms

PHOSPHORUS CYCLE

The weathering of rocks makesphosphate ion available in soils.

Plants take up phosphate fromthe soil and is incorporated intoorganic molecules.

Animals eat plants andincorporate some of thephosphate.

Decomposition of deadorganisms return the inorganicphosphate ion to the soil.

Some of the phosphate in soilruns off into ocean andincorporated into sediments overtime.

PHOSPHORUS CYCLE

1

2

3

4

5

1

2

3

4

5

2.5 POPULATION ECOLOGY

• Explain the biotic potential and environmental resistance and their effect on population growth

• Explain carrying capacity and its importance

• Describe natality and mortality and their effects on the rate of population growth

Biotic Potential (r)• Refers to the ability of its individual

organisms to survive and reproduce under optimum conditions.

• Actual capacity of a natural population will only reach biotic potential if all the individuals in the population survive and reproduce at the maximum rate.

• Full biotic potential is reached if environmental resistance is absent.

• Produce exponential growth or J shaped curve.

8,000

6,000

4,000

2,000

0

1920 1940 1960 1980

Year

Ele

ph

an

t p

op

ula

tio

n

1900

• Depends on several factors:

• The age beginning of reproduction

• How often reproduction occurs

• How many offspring are born at a time

Environmental Resistance• Refers to the biotic and abiotic

factors that oppose the achievement of biotic potential by a population

• Limits the size of a population

• When populations become large, they tend to run out of some limiting resources such as food, water, light, oxygen and space.

• The growth rate slows down to zero and the population size tens to stabilized producing S shaped curve

Carrying Capacity (k)

• Total number of organisms that can be supported by the environmental resources in an ecosystem

• The area occupied by a population has limit the resources and this limits the population growth by maintaining an equilibrium between natality and mortality rate.

Carrying Capacity (k)

• Population increases until it reaches saturation within the carrying capacity of its ecosystem.

• The carrying capacity of an ecosystem is not constant as it is affected by environmental conditions.

Carrying Capacity : Importance

• Important limit on population

• A population below carrying capacity need not deplete any natural capital (e.g: food)

• Unchecked growth of any species will exceed carrying capacity

• No population can live beyond carrying capacity for very long time.

Factors Affecting the Rate of Population Growth : Natality and Mortality

• As long as resources are available, every population has the tendency to grow exponentially. Population growth is affected by:

• Natality (birth rate)

• Ratio of birth to the general population

• Mortality (death rate)

• Ratio of the total number of death to the total population

• Effect on population growth:

• Natality rate > mortality rate?

• Natality rate < mortality rate?

• Natality rate = mortality rate?