Ecology

‣ Ecology is the study of the relationships between organisms and their physicaland 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 ofcomplexity.

‣ 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 troposphere.

The Biosphere

Image: NASA

‣ Our knowledge of what constitutes the biosphere continues to develop as scientists continue their exploration of the Earth.

‣ As we learn more about the biosphere, we find new kinds of life in areas we previously thought were lifeless!

Exploring the

Biosphere

Life exists in all places, from blind white crabs

in 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°C

The 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°C

The 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 forestsare 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 cm

Ample 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 Argentina

The South African veldt

The Great Plains of the USA

‣ Grasslands are highly productive and large regions have been converted to agriculture.

Temperature range: 24°C

The 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 biomedistribution. Temperature decreases from the equator to the poles.

Arctic

regio

n

Subarcti

c region

Temperate

region

Tropical

region

Polar

La

titu

din

al re

gio

ns

Equatorial

Annual precipitation (mm)

Components of an Ecosystem

Community

Physical

environment

‣ A biome is a large geographical regioncomprising natural units called ecosystems.

‣ An ecosystem encompasses the physicalenvironment and the community.

Physical

environment

Community

Biotic

factorscompetitors

symbionts

predators parasites

pathogens

Ecosystem

Abiotic

factors

atmosphere

soil

water

wind speed

wind direction

current 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 environmentrefers to the physical surroundings of any organism, including:

the medium, e.g. water

substrate, e.g. soil

climatic (atmospheric)

conditions

light …

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

Ph

oto

: C

ou

rte

sy P

AS

CO

scie

ntific

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 altitude

27°C, 20%

humidity

Desert surface

45°C, <20%

humidity

Under rock

28°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 Factors

Hypothetical values for physical

factors in rock pools at different

places on a rocky shore.

Salin: 42 gl-1

Temp: 28° C

DO: 20%

Exp: 12 h

Salin: 39 gl-1

Temp: 28° C

DO: 30%

Exp: 10 h

Salin: 38.5 gl-1

Temp: 26° C

DO: 42%

Exp: 8 h

Salin: 37 gl-1

Temp: 22° C

DO: 57%

Exp: 6 h

Salin: 36 gl-1

Temp: 19° C

DO: 74%

Exp: 4 h

Salin: 35 gl--1

Temp: 17° C

DO: 100%

Exp: 0 h

Salin: salinity

Temp: temperature

DO: dissolved oxygen

Exp: 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 Factors

Light: 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 intensity

Wind: wind speed

Hum: humidity