View
59
Download
0
Category
Tags:
Preview:
DESCRIPTION
Version: 1.0. Contents. 1) Biomes Distribution of biomes Classification of biomes 2) Components of Ecosystems Components of ecosystems Factors affecting ecosystems Habitats Adaptations 3) Energy flow in Ecosystems Trophic structure Energy in ecosystems Ecosystem productivity - PowerPoint PPT Presentation
Citation preview
Version: 1.0
‣ 4) Biogeochemical Cycles
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Sulfur cycle
Water cycle
‣ 5) Ecosystem Stability
Environmental change
Key species
Ecological succession
‣ 1) Biomes
Distribution of biomes
Classification of biomes
‣ 2) Components of Ecosystems
Components of ecosystems
Factors affecting ecosystems
Habitats
Adaptations
‣ 3) Energy flow in Ecosystems
Trophic structure
Energy in ecosystems
Ecosystem productivity
Ecological pyramids
Contents
Click on the hyperlink title you wish to view
Ecology‣ Ecology is the study of
the relationships between organisms and their physical and biotic environment:
Relationships involve interactions with the physical world as well as interrelationships with other species and individuals of the same species.
O2
Nutrients
CO2
‣ Living organisms can be studied at different levels of complexity.
‣ From least to most complex, these levels are (in an ecological context):
Individual
Population
Community
Ecosystem
Biome
Biosphere
Biological Complexity
Biosphere
Biome
Ecosystem
Community
Population
Individual
• The biosphere isthe region within which all living things are found on Earth.
• It is the narrow belt around the Earth extending from the bottom of the oceans to the upper atmosphere.
The Biosphere
Image: NASA
• Our knowledge of what constitutes the biosphere continues to develop as scientists continue their exploration of the Earth.
• The biosphere extends into the Earth’s crust, below the oceans and deep into rock fissures; it extends well into the Earth’s upper atmosphere.
Exploring the Biosphere
Life exists in all places, from blind white crabsin lightless environments...
to tube worms in the crushing ocean depths.
• The biosphere encompasses all living things on Earth.It comprises a number of aquatic and terrestrial biomes.
• Biomes are the largest geographically based biotic communities that can be conveniently recognized.
• Biomes within the same category have specific, characteristic features.
Biomes
Desert biome
• Terrestrial biomes are recognized for all the major climatic regions of the world and are classified on the basis of their predominant vegetation type.
The same biome may occur in widely separated regions.
Terrestrial Biomes
• Three air cells circle each hemisphere of the Earth.The interaction of these cells is a major contributor the formation of biomes.Biomes and Weather Cells
Dry air descends at the poles
Polar cell
Air rising at the equator causes the
formation of rain clouds
Rising air allows cloud formation in temperate regions
After losing its moisture, dry air
descends
Hadley cell Ferrel
cell
Polar Temperate Desert Tropical Desert Temperate Polar
• Deserts are arid regions (annual rainfall generally less than 25 cm). The hot desert biome is found in two belts, centered at 30° latitude north and south of the Equator.
• Hot deserts receive most of their rainfall in summer. The driest regions are in central Australia and the middle of the Sahara Desert.
The temperature range is approximately 30°C, and the winter and summer are both very warm.
Hot Deserts
Ayres Rock, Australia Sand dunes, Namibia
Temperature range: 9°CThe winter and summer are both very warm.
Annual total rainfall: 15 cm
Example: Khartoum, Sudan 15.5°N
Physical Factors:Hot Deserts
Khartoum
• The cold desert biome is found in dry regions in the mid to high latitudes, especially in the interiors of large continents. Cold deserts also occur at high altitudes in the rain shadows of mountain ranges.
• Cold deserts receive most of their small amount of rainfall in winter.
Cold Deserts
Arches National Park, USASierra Nevada, USA
Example: Cheyenne, Wyoming 41°N
Temperature range: 23°CThe winters are cold; summers are much warmer.
Annual total rainfall: 38 cm
Physical Factors:Cold Deserts
Cheyenne
‣ Tropical savannas are found in central and eastern Africa, and in tropical and subtropical regions of South America and Australia. Thorn forests are found on the equatorial sides of hot deserts.
• Both have mild, dry winters and mild, wet summers.
Unlike savanna, thorn forests generally lack grasses. This reflects the increased aridity of the climate.
Savanna & Thorn Forests
Temperature range: 10.7°C
Annual total rainfall: 74 cm
Example: Kayes, Mali 14°N
Physical Factors: Savannas
Kayes
• Tropical evergreen forests are found in equatorial regions where total annual rainfall exceeds 250 cm and the dry season lasts for no more than 2-3 months. These forests are species-rich.
• The climate is warm and rainy all year round.
Tropical Rainforests
Rainforest, Central America
Temperature range: 2.2°C
Annual total rainfall: 262 cm
Example: Iquitos, Peru 3°S
Physical Factors: Tropical Rainforests
Iquitos
Temperate Forests• Temperate forests occur
throughout mid latitudes where there is a high annual rainfall.
• Temperate forests are usually deciduous, but where seasonal fluctuations are moderated by proximity to the coast, the forests are evergreen and are termed temperate rainforests.
Temperate rainforests occur in south-eastern Australia, New Zealand, along the Pacific North-West coast of the United States.
Temperate deciduous forest
Temperate rainforest
Physical Factors:Temperate Forests
Temperature range: 31°C The temperature fluctuates dramatically between summer and winter.
Total annual rainfall: 81 cmAmple falls throughout the year.
Example: Madison, Wisconsin 43°N
Madison
Temperate Grasslands• Temperate grasslands
or prairies occur in mid latitudes, in regions that are relatively dry for much of the year. They occur in many parts of the world, and include:
The Pampas of ArgentinaThe South African veldtThe Great Plains of the USA
• Grasslands are highly productive and large regions have been converted to agriculture.
Temperature range: 24°CThe temperature fluctuates widely, with hot summers, cold winters.
In some grasslands, most precipitation occurs in the winter. In others, the majority falls in summer.
Total annual rainfall: 31 cm
Example: Pueblo, Colorado 38°N
Physical Factors:Temperate Grasslands
Pueblo
• The tundra biome is found in the Arctic and high in the mountains at all latitudes. It is dominated by low-growing perennial plants.
The Arctic tundra is very wet even though rainfall is low and this is because the water cannot drain down through the permafrost (permanently frozen ground).
Tundra
Tundra: northern Canada
Arctic tundra
Temperature range: 28°C
Total annual rainfall: 23 cm
Example: Greenland 73°N
Physical Factors:Tundra
Greenland
• Mountainous regions are associated with their own altitude adapted vegetation.
• The icy regions of the polar ice caps (the Arctic and Antarctic) form sheets of ice that extend into and over the sea.
Mountains and Ice
Predicting Biome Distribution 1• Temperature and precipitation are excellent
predictors of biome distribution. Temperature decreases from the equator to the poles.
Arctic region
Subarctic region
Temperate region
Tropical region
Polar
Latit
udin
al re
gion
s
Equatorial
Annual precipitation (mm)
Predicting Biome Distribution 2• Temperature and precipitation act together as limiting factors to determine the
type of desert, grassland, or forest biome in a region.
Components of an Ecosystem
Community
Physical environment
• A biome is a large geographical region comprising natural units called ecosystems.
• An ecosystem encompasses the physical environment and the community.
Physical environment
Community
Biotic factorscompetitors symbionts predators parasites
pathogens
EcosystemAbiotic factors
atmospheresoil
water
wind speed
wind directioncurrent velocity
Ecosystems Light intensity varies
Flow rate varies Rainfall level varies
• An ecosystem includes:
all of the organisms(the community) … and their physical environment.
• There are many different sorts of ecosystems from natural to artificial, and they range in size from large to small.
Still water habitatFast flowing water habitat
Rock habitat Stream bank habitat
• A community is a naturally occurring group of organisms living together as an ecological entity; the biological part of the ecosystem.
Communities
A nudibranch snail feeding on rock
encrusting organisms
Environments
• The physical environment refers to the physical surroundings of any organism, including:
the medium, e.g. watersubstrate, e.g. soil climatic (atmospheric) conditionslight …and other physical properties.
• The type and extent of vegetation in a particular ecosystem is determined by physical factors on both a large scale and on a very localized (microclimate) level.
Vegetation patterns are governed largely by climate (which is broadly related to latitude) and altitude.
Climate and Vegetation
High latitude climate
Temperate climate
‣ Abiotic (physical) factors are the influences of the non-living parts of the ecosystem.
Examples include pH, salinity, temperature, turbidity, wind speed and direction, humidity, precipitation, water pressure, and light intensity and quality.
‣ Biotic factors are the influences of the living parts of the ecosystem. Producers and consumers interact as competitors, parasites, pathogens, symbionts, and predators.
Factors Affecting Ecosystems
• Devices for measuring the physical factors in the field include the following meters:
Quantum light meter
Dissolved oxygen
Oxygen meter
pH meter
Total dissolved solids (TDS) meter
Current meter
Multi-purpose meter
Hygrometer
Wind meter
Other equipment includes:
Secchi discs
Nansen bottles
Monitoring Physical Factors
Pho
to: C
ourte
sy P
AS
CO
sci
entif
ic
Pasco datalogger with attached sensor
‣ Gradients in abiotic factors are found in almost every environment.
They influence habitats and microclimates, and determine patterns of species distribution.
• The effects of these physical (or environmental) gradients are particularly evident where physical conditions change markedly within a short distance, e.g. in deserts, along rocky shores, in lakes and tropical rainforests, and on mountains.
Physical Gradients
‣ Desert environments experience extremes in temperature and humidity, but they are not uniform with respect to these factors.
Physical conditions vary widely within the one general environment. Crevices, burrows, and the presence of rock overhangs and vegetation create microclimates where extremes in physical conditions are reduced compared to the desert surface.
Desert Environments
Desert Factors
1 m above ground
33°C, 20% humidity
300 m altitude27°C, 20% humidity
Desert surface45°C, <20% humidity
Under rock28°C, 60% humidity
Burrow(2 m underground)25°C, 95% humidity
Crack/crevice(1 m underground)27°C, 95% humidity
Hypothetical values for temperature (°C) and percentage humidity at midday in a desert environment.
• Rocky shore environments typically exhibit marked physical gradients as a result of tidal movements. Horizontal and vertical gradients in salinity, temperature, dissolved oxygen, and exposure time are reflected in the communities found at different positions on the shore.
Horizontal: from the low tide to the high tide marks
Vertical: from the bottom to top surfaces of rocks and boulders.
Rocky Shore Environments
Rocky Shore FactorsHypothetical values for physical factors in rock pools at different
places on a rocky shore.
Salin:
42 gl-1
Temp:28° CDO: 20%Exp:12 h
Salin:
39 gl-1
Temp:28° CDO: 30%Exp:10 h
Salin: 38.5 gl-1
Temp: 26° CDO: 42%Exp:8 h
Salin: 37 gl-1
Temp: 22° CDO: 57%Exp:6 h
Salin: 36 gl-1
Temp: 19° CDO: 74%Exp:4 h
Salin: 35 gl--1
Temp: 17° CDO: 100%Exp:0 h
Salin: salinityTemp: temperatureDO: dissolved oxygenExp: exposure time
(per 12 hour tidal cycle)
• The high species diversity of tropical rainforests can be supported because of the wide variety of microhabitats provided by the layered structure of the forest.
• The physical conditions at the uppermost level are quite different to those at the forest floor with respect to light intensity (and quality), wind speed, and humidity.
A Tropical Rainforest
Canopy
Subcanopy
Understorey
Ground layer
Rainforest FactorsLight: 70%Wind: 15 kmh-1
Hum: 67%
Light: 50%Wind: 12 kmh-1
Hum: 75%
Light: 12%Wind: 9 kmh-1
Hum: 80%
Light: 6%Wind: 5 kmh-1
Hum: 85%
Light: 1%Wind: 3 kmh-1
Hum: 90%
Light: 0%Wind: 0 kmh-1
Hum: 98%
Light: light intensityWind: wind speedHum: humidity
‣ Oxbow lakes are formed from old river meanders that have been cut off and become isolated from the main channel following the change in the river’s course.
Occasionally they may be deep enough to develop temporary, but relatively stable, gradients in physical factors from the surface to the bottom of the lake.
Oxbow Lakes in Summer
Oxbow Lake Factors
Zone of mixing
Temp: 16°COxy: 5.2 mgl-1
Light: 10%
Temp: 24.6°COxy: 9.2 mgl-1
Light: 100%
Temp: 12.5°COxy: 0.2 mgl-1
Light: 2.5%
Temp: 13°COxy: 3.4 mgl-1
Light: 5%
Temp: 22.1°COxy: 9.7 mgl-1
Light: 25%
Habitat• The ecological niche describes the functional position of an organismin its environment.
• A niche comprises:
the habitat in which the organism lives.the organism’s activity pattern: the periods of time during which it is active.the resources it obtainsfrom the habitat.
Ecological Niche
Adaptations
Activitypatterns
Presence of other organisms
Physicalconditions
• The fundamental niche of an organism is described by the full range of environmental conditions (biological and physical) under which the organism can exist.
• The realized niche of the organism is the niche that is actually occupied. It is narrower than the fundamental niche.
This contraction of the realized niche is a result of pressure from, and interactions with, other organisms.
The Fundamental Niche
• The physical conditions influence the habitat in which an organism lives. These include:
substratehumiditysunlighttemperaturesalinitypH (acidity)exposurealtitudedepth
• Each abiotic (or physical) factor may be well suited to the organism or it may present it with problems to overcome.
Physical Conditions
• The law of tolerance states that “For each abiotic factor, an organism has a range of tolerances within which it can survive.”
Law of Tolerance
Tolerance range
Optimum range
Unavailable niche
Marginal niche
Num
ber o
f org
anis
ms
Preferred niche
Marginal niche
Unavailable niche
Examples of abiotic factors that influence size of the realized niche
Too acidic pH Too alkaline
Too cold Temperature Too hot
• An organism’s habitat is the physical place or environment in which it lives.
• Organisms show a preference for a particular habitat type, but some are more specific in their requirements than others.
Habitat
Lichens are found on rocks, trees, and bare ground.
Most frogs, like this leopard frog, live in or near fresh water, but a few can
survive in arid habitats.
• An organism’s habitat is not always of a single type. Some organisms occupy a range of habitats. There are various reasons why:
Highly adaptable in habitat requirements. Different, but equivalent, resources available in different habitats.Reduced competition for resources in sub-optimal habitats.
• Habitat extremes may influence growth form, especially in plants.
Habitat Range
• Organisms may select particular areas within their general habitat, even in apparently homogeneous environments, such as water.This is termed habitat preference.
Example: Aquatic organisms may show a preference for a particular substrate type, water depth or velocity, water clarity, or degree of vegetation cover or habitat disturbance.
• Knowledge of habitat preference can be used to protect species in their environment.
Habitat Preference
Damselfly nymph
Rainbow trout
Recommended