Chapter 4Climate and Biomes

Atmosphere

Weather is short term conditions of atmosphere

Climate is long term conditions

5 major processes influence climate/weather: unequal heating of earth, convection currents, Coriolis effect, tilt, and oceans

Atmosphere has 4-layers:

1. Troposphere (0-20km): bottom layer, densest, where most weather and mixing occurs, temps get colder with height

2. Stratosphere (20-50km): second layer, gets warmer with height, contains ozone layer that absorbs UV light

3. Mesosphere (50-80km) – third layer, coldest, meteorites burn up

4. Thermosphere – top layer, warmest, absorb gamma rays

Atmosphere protects organisms from radiation and it regulates temperatures

1. Unequal HeatingAtmosphere is heated unevenly for 2 reasons

1. Tilt of the earth

2. Some areas on earth reflect more sunlight than other areas (albedo)

White surface has higher albedo than black surface

This uneven heating of the atmosphere drives convection currents in the atmosphere

2. Atmospheric Convection CurrentsAir has 4 properties that determine how it will circulate

1.Density: less dense air rises (warm), more dense air sinks (cold)

2.Water vapor capacity: warm air can hold more water vapor (saturation point) which is less dense

3.Adiabatic heating/cooling:

1. When air rises, pressure decreases and air expands and temps lower due to less friction between air molecules

2. When air sinks, pressure increases and air compresses and temps rise due to more friction between air molecules

4.Latent heat release: when air condenses, the energy that evaporated it is released and air warms

(2). Formation of Convection Currents

• Air rises in warm, moist tropics

• Rising air experiences lower atmospheric pressure and adiabatic cooling until it reaches saturation point

• This leads to condensation which releases latent heat

• Eventually air cools and spreads out and begins to sink around 30⁰ latitude (deserts)

• When sinking air hits the ground, it spreads in all directions completing the cycle, called a Hadley cell

• Air re-converges at the equator, called the intertropical convergence zone (ITCZ)

• Polar regions cause additional Hadley cells

3. Earth’s Rotation and Coriolis Effect

Earth rotates faster at equator than poles

Objects’ paths get deflected due to the rotation of earth. This is known as the Coriolis effect

This deflects winds and sets up weather patterns

Trade winds blow towards the equator between 0- 30°. They meet at the equator and rise creating calm winds called the doldrums

Where the air sinks at 30° is the horse latitudes

Air moves north from here, Coriolis force deflects it to right, and get westerlies (40°-60°)

At poles, the air sinks and moves towards the equator, but gets deflected to right. This creates polar easterlies

4. Earth’s Tilt and Seasons• Earth is tilted 23.5⁰

• When northern hemisphere is pointed towards the sun they experience summer

• When northern hemisphere is pointed away from the sun they experience winter (southern hemisphere is opposite)

• Vernal/automnal equinoxes, everywhere receives 12h daylight

• Poles have 6 months of darkness and 6 months of daylight

5. Ocean Currents• Currents driven by temp, gravity, prevailing winds, Coriolis

effect, and continents

• Water is warmer at the equator, so it expands and rises. This makes the water higher then the rest of earth and gravity takes over

• Winds and Coriolis effect start ocean currents and deflect them. Called gyres (transport heat)

• Upwelling (rising of water) occurs along coastlines

• Thermohaline circulation is when water is saltier, making it more dense, so it sinks

• ENSO (El Nino – Southern Oscillation– when ocean currents change direction, thus affecting climates

Rain Shadows• Air rises on one side of a mountain range and

moisture condenses out

• On other side, air sinks preventing clouds and it remains dry

• Dry region is called a rain shadow

Altitudes create “latitudinal” patterns• Vegetative communities rapidly change

along mountain slopes

• The climate varies with altitude

• A mountain climber in the Andes • Begins in the tropics and ends

on a glacier

• Rainshadow effect = air going over a mountain releases moisture• Creating an arid region

on the other side

Biomes• Biomes are large regions characterized by a specific

type of climate and certain types of plant and animal communities

• Largest category scientists use to classify ecosystems

• Each biome has many ecosystems

• Biomes described by vegetation because that determines organisms and amount of vegetation is determined by climate

• At altitude and latitude increase, temps decrease

Tundra Climate: Very cold year around and little precip (driest biome)

Location: North of the arctic circle

Plants:

1. Mostly mosses and lichen (which don’t need soil)

2. Rest of plants are low and have wide roots to keep them stable in winds

3. Soil is permafrost which makes it hard for trees to grow, and low in nutrients

Animals: Birds common in summer, caribou, wolves, deer, rabbits, foxes, bears

Threats: Oil excavation and pollution. Food chain is simple, so small change has dramatic consequences

Other: CO2 sink, none in southern hemisphere

Boreal Forest (taiga)Climate: Long cold winters, short mild summers, and

fairly dryLocations: Just below the arctic circleVegetation (slow decomposition allows for little):

1. Dark forest floor because thick canopy blocks sunlight

2. Branches near tops of trees

3. Trees are conifers (seeds in a cone)

4. Leaves thin, pointy, and waxy to store water and shed snow

Animals:1. Many insects in summer

2. Migratory birds to feed on insects

3. Some large herbivores and thick-coated carnivores

Threats: global warming and oil excavation Other: soil low in nutrients, lots of lakes from last ice age

Temperate Rain Forest and Temperate Deciduous Forest

Climate:

1. Temperate rain forest = wet year around with moderate temps

2. Temperate deciduous forest = Moderate precip and large temp range (4-seasons)

Location: TRF = northwest US, TDF = Mid latitudes

Plants:

1. TRF = Draped with mosses, lichens, and ferns

2. TDF = Many tall trees and many shrubs since plenty of light. Lose leaves

Animals:

1. Many animals and insects

2. In TDF, many animals fly south or hibernate and shed fur

Threats: overdevelopment, logging, fossil fuels, agriculture

Woodland/Shrubland Chaparral

Climate: Dry and warm, but not quite desert dry

Location: Mostly around 30° latitude near water

Plants:

1.Many evergreen shrubs

2.Plants oily to burn and to retain water

Animals: most animals camouflage, many have scales, and most small

Threats: human development

Other: wild wild west

Tropical Rain Forest

Savannah Separate desert biomes from tropical rain forest biomes

Climate: Short wet season, long dry season, and warm year round

Location: Close to the equator

Plants:

1. Full of grasses (many sharp and bitter) with scattered trees

2. Trees have large horizontal roots to absorb water in dry season and thick bark to survive fires

Animals:

1. Full of grazing animals and their predators

2. Herbivores have many heights to limit competition

3. Many have long legs or wings to migrate

Threats: poaching, hunting, agriculture, grazing

Other: Many grassfires

Temperate GrasslandsClimate: Hot summers, cold winters, and inconsistent precipitation

Locations: Interior of continents, often surrounded by mountains which limit rainfall

Plants:

1.Very fertile soil

2.Many grasses and flowers which are perennials

3.Prairies = tall grasses (wetter) Steppes = short grasses (drier)

4.Very few trees because limited rainfall

Animals: Many smaller animals that can hide in grass and their predators

Threats: over farming

DesertClimate: very dry and mostly warm to very hot year around (with

large daily temp range)

Location: Most around 30° latitude

Plants: 1. Little to no vegetation

2. Plants called succulents have thick, fleshy stems to store water (cactus).

3. Spines keep thirsty animals away and conserve water

Animals:1. Animals are mostly small reptiles, spiders, and insects

2. Most have shells or scales to trap water in

3. Most bury themselves underground

4. Most nocturnal

Other: 1. Soil rich in minerals but low in nutrients2. Can be cold

Aquatic Ecosystems• Aquatic ecosystems are categorized by salinity, depth,

nutrients, and water flow

• Streams and rivers: rivers larger and carry more water. Very little plant matter (most washes from land). Slower they flow typically means more life

• Lakes and ponds: have standing water that gets too deep to support rooted plants. Lakes typically larger and have water flowing in an out• Littoral zone: shallow area near shore. Algae and cattails. Most life

• Limnetic zone: not rooted plants. Phytoplankton are producers. Extends as deep as sunlight penetrates

• Profundal zone: region below where sunlight reaches. Not productive (few decomposers)

• Benthic zone is the muddy bottom (low temps and oxygen levels)

Freshwater Wetlands• Wetlands are land covered with water during

parts of the year

• Most found in the southeastern US

1. Filter pollutants and sediments

2. Prevent flooding by storing excess water

3. Provide homes for many types of organisms

4. Recycle nutrients and sinks (CO2)

2-types: marshes and swamps

• Marshes do not contain woody plants

• Swamps contain woody plants

• Low oxygen levels, so slow decay

Salt Water WetlandsAn estuary is where freshwater meets saltwater. Very productive ecosystem with large biodiversity:

1. Many nutrients trapped where currents meet

2. Tides circulate nutrients

3. High level of light penetration

4. Many plants in and around

Salt marsh is a muddy wetland near estuary where nutrients pile up

•Dry during low tide, wet during high tide

•Mangrove swamps are swamps in tropical areas that are dominated by mangrove trees. Protect shore from erosion and provide shelter

•Rocky shores have many more plants and animals than sandy ones.

Coral Reefs• Coral reefs are limestone ridges built by tiny animals

• It is made of skeletons that accumulate (limestone)

• Found in shallow, tropical water

• They eat microscopic organisms with tentacles

• Symbiosis with algae (coral release CO2, algae uses that for photosyn and creates sugars that coral uses)

• One of most diverse ecosystems in world

• If water temp or salinity changes, they can die

• Oil spills, sewage, pesticide, runoff, harvesting (for jewelry) and over fishing have killed reefs

The Open Ocean• The depth that light can penetrate in the

open ocean is dependent on the amount of sediment and algae suspended in the water.

• Photic zone- the zone that receives enough light to allow photosynthesis to occur.

• Aphotic zone- the deeper water that lacks sufficient light for photosynthesis.

• Chemosynthesis- The process that occurs in the aphotic zone when some species of bacteria use methane and hydrogen sulfide to generate energy.