chapter 4 environments and life sir david ochieng

Chapter 4

Environments

and Life

Sir David Ochieng

www.davidochieng.net

What is your current classification?

A. Freshman

B. Sophomore

C. Junior

D. Senior

Guiding Questions

• What factors determine the ecological niches of species, and by what means do species obtain nutrition?

• What factors govern the geographic distribution of species?

• What factors govern the distribution of aquatic life?

Environmental Differences

• Tropical vs Polar - Terrestrial and Marine

• Low vs High Elevation

• Shallow vs Deep

• Wet vs Dry

Hypsometric Curve

• Curve showing the proportions of the Earth’s surface above and below sea level

Hypsometric Curve

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Climate

• Climate– Controls distribution of species globally– Has changed through time

• Plate tectonics and other changes affect climate

Ecology

• Ecology– Study of the factors that govern the distribution and

abundance of organisms in natural environments• Habitats

– Environments on or close to Earth’s surface inhabited by life• Terrestrial• Aquatic

– Marine– Freshwater

Ecology• Ecologic niche

– The way a species relates to its environment, including food, nutrients, physical and chemical conditions

• Life habit– The way a species lives within its niche

• Limiting factors– Naturally occurring, restricting condition (physical and chemical)– Competition

• Shared drive for limited resources– Predation

Competition

Arises because organisms share space

Predation also comes in here by possibly limiting or preventing another species from inhabiting a particular environment.

Ecosystem

• Ecosystem– Organisms of a community and the physical

environment they occupy

• Population– Group of individuals that belong to a single

species and live together in a particular area

Ecosystem

• Ecologic community– Populations of several species living in a habitat

• Producers– Photosynthesizing organisms; foundation of

community

• Consumers– Herbivores: feed on producers– Carnivores: feed on other consumers

Ecosystem• Biota

– Fauna: animals and protozoans of an ecosystem– Flora: plants and plantlike protists

• Food chain– Sequence of consumption for producers to consumers

Food Web

• Food web– More complex than simple food chain

• More common

– Several species occupy each level

Ecosystem• Parasites

– Feed on living organisms

• Scavengers– Feed on organisms that

are already dead

Ecology

The movement of materials through an ecosystem. Components within ovals are consumers.

Figure 4-35 (p. 134)

Interdependence of photosynthesis and respiration.

Figure 4-38 (p. 136)Simple pyramid of ocean life.

Biogeography

The distribution and abundance of organisms on a broad geographic scale.

Biogeography

• Temperature

• Moisture

• Nutrients

Ecosystem• Diversity

– The variety of species that live together within a community• Lower in more difficult habitats• Predation influences diversity

– Heavy can reduce diversity– Moderate can increase diversity by reducing competition

• Opportunistic species– Species that specialize in invading newly vacated

habitats

Biogeography

• Distribution and abundance of organisms on a broad geographic scale

• Limiting factors– Diversity increases

toward equator– Barriers can affect

dispersal

Life Habitats

The mode by which an organism lives, feeds in an environment

1. Tropical vs. Polar

2. Low vs high altitude

3. Shallow vs deep

4. Benthic vs. Planktonic

Atmosphere• Regulates Earth’s

temperature (-18°C w/o atmosphere)

• Composition– N2, O2, CO2

• Tilt of the Earth affects solar insulation, temperature, and climate

In our present atmosphere, concentrations of O2 and CO2 are:

A. O2 > CO2

B. O2 < CO2

C. O2 = CO2

The Atmosphere

• Nitrogen -78%

• Oxygen - 21%

• Carbon dioxide (CO2 ) - 0.037% or 370 ppm

• Methane (CH4) - 0.00018% or 1800 ppb

Solar Radiation

Daylight

Which receives more hours of daylight?

Equator vs Poles

The amount of daylight (# of hours) averaged over a year is the same at the poles as at the equator

Solar Radiation

Solar Radiation

• Temperature difference is due to the angle of the sunlight and the albedo

• In the high latitudes, the sun hits at a low angle and therefore the unit energy of sunlight is spread over a large cross-sectional area of the earth’s surface. In the tropics, the sun hits directly and therefore is much more concentrated

Solar Radiation

Solar Radiation

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Albedo refers to the reflectivity of the Earth’s surface

1. Snow and ice is very reflective - much of the solar radiation is reflected by to the solar system

2. Water has a low albedo and absorbs a lot of the solar radiation

Solar Radiation

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Solar Radiation

Solar Radiation

• When do we have summers?

• True or False

• Summers on Earth occur when it passes closest to the Sun

Solar Radiation

• Obliquity or Tilt (23.5°) of the to Earth’s rotational axis

• This tilt gives us seasons. Summer is when the northern or southern hemisphere is point towards the Sun

Atmosphere• Regulates Earth’s

temperature• Composition

– N2, O2, CO2

• Tilt of the Earth affects solar insulation, temperature, and climate

Solar RadiationHeat Capacity

Movement of Air mass

• Rises at Eq. and sinks near Poles

• The high solar radiation at the equator heats the air masses, causing them to rise (buoyant).

• As the air rises, the temperature of the air mass decreases

Atmospheric Circulation

• Net transport– Air sinks at the poles,

rises at the equator

– Simplified model• No tilt• No Coriolis effect

Rising Air QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

As the air rises, the temperature of the air mass decreases (adiabatic lapse rate 5°C/km)

Cold air holds less water vapor. Voila, rain and the tropical rainforest. Low pressure systems usually have rain because the rising air drop water as the air ascends and cools

Rising Air

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Atmospheric Circulation

• Coriolis effect • Earth’s rotation causes

air and water masses to be defected to the right (clockwise) in the northern hemisphere – Counterclockwise for

southern hemisphere

Atmospheric Circulation

• If we reverse the direction and launch a rocket from Panama towards Washington DC, which way will it curve?

• A = Right• B = Left• C = Not at all because

Panama is close to the Eq.

Coriolis force

• Deflection of moving objects to the right in the No. Hemisphere and left in the So. Hemisphere

Coriolis Force

Atmospheric Circulation

• Actual pattern is more complex– Three circulation cells– Trade winds, westerlies,

easterlies

• Intertropical convergence zone– Northern, southern trade

winds converge near equator

• Changes seasonally

Temperature Variations

• Atmosphere retains heat

• Solar radiation– Absorbed and turned

into heat energy– Reflected

• 6-10% ocean• 5-30% forest• 45-95% ice and snow

Trade winds

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• As the dry air descending around 30° begins to flow back towards the Eq. it is deflected to the right.

Trade windsAs the dry air descending around 30° begins to flow back

towards the Eq. it is deflected to the right.

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Trade windsThe NE and SE trades converge on the

latitude where the maximum in convection (rising air) is occurring. This

is the warmest location. Today, this is between 4 and 10°N and is termed the

Inter-Tropical Convergence Zone (ITCZ)

The Terrestrial Realm

• Latitudinal Zones and Vegetation• Rain forests • Deserts • Savannah Grasslands • Temperate Forest • Conifer or Evergreen Forest• Tundra

Terrestrial Realm• Vegetation follows

climatic zone– Tropical rain forest – Desert savannahs– Temperate forests– Polar tundra

Terrestrial Realm

• Tropical Climates– 18–20° C (64–68° F)– 0–30° latitude

• Tropical Rain Forest– Dense vegetation

Rain forests

• develop under the tropical low pressure systems. Rising air dumps lots of rain. Found within a few degrees near the equator

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Terrestrial Realm

• Deserts– Dry trade winds

remove moisture– 20–30° north and south

of the equator– < 25 cm rain/year– Little vegetation

• Savannah, grasslands– Too dry to support

forests

Deserts• (<10 inches of water per year) develop under the sinking dry air masses and under the dry Trade Winds. Usually found around 30° latitude.

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Savannah Grasslands

• found between Rain forest and Desert and receive seasonal rain falls. Not enough rain throughout the year to support woodland

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Tundra

- Arctic ecosystem where layer beneath soil remains frozen throughout the year.

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Terrestrial Realm

• Poles– Defined by ice sheets

and glaciers today– Absent or reduced at

times in the past

Terrestrial Realm

• Glaciers– Ice in motion– Glide and spread– Present at high

latitudes and high elevations near equator

Terrestrial Realm

• Tundra– Limited water– Grasses, sedges, lichens,

shrubs dominate– Cannot support tall trees

• Evergreen coniferous forests– South of tundra– Spruce, pine, fir

Terrestrial Realm

• Temperate forests– Longer summers, slightly warmer– Deciduous trees

• Maples, oaks, beeches

• Mediterranean climate– Dry summers, wet winters– Common 40° N and S of equator

• Californian, Mediterranean region

Climate

• Altitude– Similar to latitudinal

gradient– At base

• Deciduous forest

– On slopes• Evergreen forest• Tundra above tree-line

– At top• Glaciers

Climate

• Mountains• Rain shadow

– Prevailing winds bring moisture

• Precipitation on windward side

• Aridity on leeward side– Rain shadows common

on east side of North American mountain chains

Climate

• Seasonal Change– High heat capacity of

water• Less change in ocean

temperatures than on land

• Monsoon Circulation– Summer winds flow

onshore; bring rain– Winter winds offshore

Plants as Climate Indicators

• Sensitive indicators of change– Cycads

• Tropics and subtropics today

• Fossil distribution allows reconstruction of climate patterns

Plants as Climate Indicators

• Leaf Margins– Tropics

• Smooth, waxy margins

– Temperate climates• Jagged margins

Marine Realm• Ocean currents

– Wind driven– Follow atmospheric patterns

• Trade winds– Push waters west; form

equatorial currents– Equatorial countercurrents

• Return flow• Gyres

– Clockwise in Northern Hemisphere

– Gulf Stream

Marine Realm

• Circumpolar current– Circles Antarctica– Very cold

Marine Realm

• Polar circulation– Sea ice leads to more

saline water– Cold, dense waters

sink– Antarctic waters

• Flow north at depth

– Arctic waters• Flow south at depth

Marine Realm

• Ocean circulation– Waves

• Surface waves– Wind driven– Break when seafloor interacts at shallow depths

– Tides• Cause major movement of water in oceans• Due to rotation of solid Earth beneath bulges of

water produced by gravitational attraction of the moon

Marine Realm

• Continental Shelf– Submarine extension of

continental landmass

• Shelf break– Edge of shelf

• ~200 m w.d.

• Continental Slope• Continental Rise• Abyssal Plain

Figure 4-31 (p. 131)Classification of marine environments.

(After Hedgspeth, UJ. W., ed. 1957. Treatise of Marine Ecology and Paleoecology. Geological Society of America Memoirs 67(1): 18.)

The Marine Realm• The depth of the Sea • Moving from the beach seaward, one crosses a

consistent pattern of water depth changes. The continental shelf extends from the shoreline to the continental shelf break. Water depths over the shelf vary from 0 to ~200 m. This environment is very important for benthic communities because the photic zone in the ocean extends only down to 200m. Consider the implications for primary production

The Marine Realm

• The Shelf break marks the distal edge of the shelf where seaward of this point, water depths increase at a greater rate (3 to 5°slope) compared with the shelf (1 to 2°slope).

The Marine Realm

• Continental Slope. • Typically, the slope extends down to 3000

to 3500 m. Near the base of the slope is the transition from continental to oceanic crust.

The Marine Realm

• The Slope gives way to the Continental Rise. This is a less steep surface that segways to the Abyssal Plain (the ocean floor). The Rise is created as sediments are transported down the slope in turbidity currents.

The Marine Realm

• At the base of the slope and out on the abyssal plain, the slope decreases significantly and the sediments are dropped, forming the Rise

Figure 4-31 (p. 131)Classification of marine environments.

(After Hedgspeth, UJ. W., ed. 1957. Treatise of Marine Ecology and Paleoecology. Geological Society of America Memoirs 67(1): 18.)

Marine Realm

• Near shore– Barrier islands– Marshes– Epicontinental seas

Marine Realm

• Photic Zone– Region of ocean where enough

light penetrates to permit photosynthesis

• Pelagic life– Plankton

• Phytoplankton• Zooplankton

– Nekton• Benthic life

– Suspension feeders– Deposit feeders

Marine Realm

• Marine Biogeography– Tropical– Subtropical– Transitional– Subarctic

Figure 4-36 (p. 135)Major ocean surface currents.

Marine Realm

• Corals– Most require warm water– Common in tropics

• Reef builders– Coral polyp– Builds coral cup– Connected to other polyps

• Symbiotic relationship with algae

Marine Realm• Salinity

– Limiting factor near shore– Oceanic

• 35 ppt

– Brackish• Lower than marine• Bays, lagoons

– Hypersaline• Higher than marine• Hot arid climates

The portion of the temperature-depth curve in the ocean that shows maximum change is the thermocline.

Deep Water Circulation

Atmospheric Circulation

• If we reverse the direction and launch a rocket from Panama towards Washington DC, which way will it curve?

• A = Right• B = Left• C = Not at all because

Panama is close to the Eq.