Agenda 1/4

• Bell-Ringer: Name one biome and list two characteristics of that biome.

• Biome Notes

• Wrap-Up: What is the competitive exclusion principle?

Biomes: Where Do Plants and Animals Live?

Environmental Science

What is a Biome?

• A major regional community of plants and animals with similar life forms and environmental conditions.

• Largest geographical biotic unit

• Named after the dominant type of life form, such as tropical rain forest, grassland, or coral reef.

Habitat

• The geographical locations and environmental conditions where a plant or animal lives.

• Organism can find food, shelter, water, and mates to reproduce within its habitat.

Niche • Totality of a species’ environmental

requirements

– How and where an organism obtains its energy and nutrients

– Ways it interacts with other species

Competitive Exclusion Principle

• No two species can share the same exact niche indefinitely unless other factors limit the density of the better competitor.

• Natural selection favors changes that reduce the degree to which species coexist within a small area.

Example: Nitrogen in Alaska

• Species have evolved different strategies for obtaining nitrogen.

• Each species gets its nitrogen in a different form, during a different month, or from a different soil depth.

Bigelow Sedge

• Gets most of its nitrogen as nitrate during June

Dwarf Birch

• Gets most of its nitrogen as ammonium during August

Specializations

• Adaptations that are work best in a relatively narrow range of conditions.

• Opposite of generalists adaptations that are well suited for a fairly wide geographic habitat.

Adaptation Examples • Leaf Shape!

– Lots of water thin leaves w/ large surface area

• Allows leaf to capture lots of sunlight

• Looses much water through transpiration

– Little water thick stubby leaves w/ little SA

• Less surface area for minimum water loss

Banana Plant

Creosote Bush

Environmental Gradients

• Changes in conditions from one region to the next.

• Ex.) Areas of high precipitation gradually blend into areas of low precipitation.

Survival Range

• Area along a gradient where an individual can obtain just enough energy and materials to survive.

• Cannot reproduce!

Reproductive Range

• An area where individuals have enough energy for reproduction.

– Remember: the ability to reproduce is a luxury!

Distribution Determinants

• Temperature

– Length of growing season number of consecutive days during which temp remains above 0° Celsius

• Plants must produce enough energy to reproduce or store enough energy to survive until the next growing season

Distribution Determinants • Water

– Amount of water in soil determined by the rates of precipitation and potential evaporation

– Potential Evaporation: the amount of water that would evaporate if water were available

– When water exceeds PE it accumulates in soil and is available to plants

– If evaporation is greater plants close stomata to save water which halts photosynthesis

Distribution Determinants

• Sunlight

– Amount of light available is determined by latitude and local climate

– Greatest amount of sunlight between 23.5°N and 23.5°S

• Clouds can limit plant growth in this area

Tropical Rain Forests

• Located within 10° of the equator (N & S)

• Supported by warm temperatures (25-27°C, 77-80°F) and heavy rainfall (2-4 meters per year)

• Warm, not hot

• Heat is dissipated by evaporating water

Tropical Rain Forests

• Rainfall exceeds evaporation during all months creating an abundant supply of water

• Warm temps and heavy rainfall give plants their shape big, thin leaves

Competition Shapes Forest

• Competition for light gives 3D shape

• Trees grow tall to capture light

• Tree leave mingle to form a closed canopy

– Provides habitat for wide variety of animal life

– Little light reaches forest floor restricting plant growth

– Very easy to walk through

Ideal Growing Conditions

• Tons of sunshine, precipitation, and warmth

• NPP rate is among highest in the world

• Up to 300 different species of trees per single hectare

• Tree depend on bees, bats, or birds for pollination

• Very diverse in both plant and animal species

Example: The Amazon (S. America)

Example: Gondwanan Rainforest (AUS)

Tropical Dry Forests

• Located in South America, Africa, Australia, and Asia as well as on the island of Madagascar.

• Found between 10° and 25° N and S of the equator

Climate

• Hot temperatures (25-35°C)

• Abundant rainfall (1-2 meters/year)

– Highly seasonal much occurs during a 6-7 month rainy season

• Rainy season: precip. greater than evaporation, water is abundant

• Dry season: evaporation exceeds precip., water is relatively scarce

Dry Season

• At start of dry season soil begins to dry

• Leaves close stomata to conserve water

• Photosynthesis slows

• Some trees change angle of their leaves from horizontal (maximize sun) to vertical (reduces sunlight captured/heat lost)

• Other species drop leaves in dry season and regrow in rainy season

Seasonality (Wet & Dry)

• Tree height is shorter than rain forests height of trees related to rainfall

• Larger fraction of energy used to create deep roots than to grow tall

• Animals:

– Birthing or hatching in wet season = more food/water

– Some migrate to wetter areas in dry season

Fat-Tailed Dwarf Lemurs

• Hibernate to avoid dry season (up to 7 months)

• Lemur slows its basal metabolic rate and allows it body temp to fluctuate with environmental conditions

Example: Madagascar

Example: Chiquitano Dry Forest (Boliva/Brazil)

Tropical Savannas

• Located between 10° and 20° N and S

• Supported by warm temperatures (25-35°C)

• Lesser amounts of rainfall than rainforests and dry forests (less than 1 meter per year)

• Rainy season is shorter than dry forest and dry season is longer than dry forest

Wet/Dry Seasons

• Small amount of rain and long dry season give savannas their appearance

• Mostly grass with widely scattered trees

• Spacing gives tree roots room to collect water from relatively large area

• Location of trees determined by many factors: – Grazing

– Termite nests (due to nitrogen limiting nutrient)

Grasses

• Predominant plant species

• Green up during growing season and brown during dry season

• Browning caused by drying which increases fire risk

Fires • At the start of rainy season lightning strikes

can ignite large grass fires

• Burn the tops of the grasses but grasses can regrow quickly underneath

• Grow from areas below the soil surface protected from fires

• Fires give open appearance, eliminate much brush

Grazers

• Vegetation shaped by grazers

• Grazing stimulates some plants to increase photosynthetic/nutrient absorption rates

• Moderately grazed areas have higher NPP and nutrient content

Animals • Influenced by grass and seasons (wet & dry)

• Abundance of edible grass (vs. trees) supports large populations of mammalian grazers

• Many grazers have long faces creates room for the teeth that are needed to grind grass while keeping animals’ eyes and ears on the lookout for predators

Grazer Example

• Antelope

• Wildebeest

• Zebra

Predator Example

• Lions

• Leopards

• Cheetahs

Large Detritivore Food Chain

• Termites create mounds up to 6 meters high that house several million organisms

• Dung beetles feed on droppings of mammalian herbivores

– Collect dung, roll into balls, lay eggs in balls and bury them

– After hatching larvae feed on the dung

Example: Kruger Park, S. Africa

Deserts

• Found on every continent other than Antarctica

• Located at about 30° N and S of the equator

• Potential evaporation exceeds annual precipitation

Precipitation

• No set precipitation rate to define deserts

• Ex.) Sonoran Desert, AZ up to 300 mm/yr

Temperature

• Deserts can’t be defined by temperature

• Ex.) summer temps in the desert of central Mongolia rarely exceed 20°C

Vegetation • Lack of water keeps desert vegetation to a

minimum

• Most deserts support some vegetation

• Ex.) Cacti and other euphorbs

– Euphorbia (genus): Herbs, shrubs, and trees of the spurge family that have a milky juice and simple alternate leaves of no leaves, and usually petalless flowers

Cacti

• Appearance reflects selective pressures to conserve and store water

• Most are fairly round which reduces surface area across which the plant may lose water

• Conversion of leaves to spines protect the plants and their fluids from herbivores

Water Availability

• In some deserts precipitation exceeds evaporation for weeks or months

– Short period of water availability allows desert plants and animals to complete their life cycles quickly

Water Availibility

• Annual plants may grow, flower, and die in just a few weeks • Blooms seemingly overnight

Spadefoot Toad • Spadefoot toads are active for only a couple of

weeks each year

– Spend most of the year buried underground

– Come to surface when it rains, lay eggs in temporary ponds

– Tadpoles have just a few weeks to mature and store enough food to last them underground until next year

Kangaroo Rat

• Abel to go entire lives without drinking water

• Obtain water directly from their food and by converting food to energy

• Metabolizing 1 gram of fat = 1 gram of water

– Same thing with camels’ humps

Example: Saharan Desert (N. Africa)

Example: Mojave Desert, CA

Mediterranean Woodland/Scrubland

• Known as chaparral (LA), matoral (Spain), fynbos (South America), mallee (Australia), and garrigue (eastern Mediterranean)

• Found on every continent except Antarctica

• Usually between 30-40° N or S of the equator but may extend farther N or S

Typical Climate

• Mild winters, hot summers

• 250-600 mm of precipitation per year

• Little precipitation during the summer, so evaporation usually exceeds precipitation during these months

Precipitation

• Quantity and timing of precipitation shapes biomes

• Yearly precip. Is sufficient to support a limited number of trees

• Lack of summer precip. makes biomes vulnerable to fire

Fires

• Shapes many of the local plants and animals

• Due to temps remaining above 0°C year-round, most trees are evergreen

• Small leaves to cope with the dry season

• Trees often have thick bark to help them survive fires

Shrubs

• Burn easily but can sprout quickly following a fire

• Many plants native to biomes are used for herbs: rosemary, thyme, sage, oregano

– Aromatic chemicals enhance burning

• Other plant species grow and reproduce when water is available and die back during summer

Animals

• Hot, dry conditions force many local animals like snakes, rabbits, and foxes to spend part of the day underground

• Burrows also serve as protection during fires for less mobile species

• More mobile species escape fires by running

Animals

• Larger grazers (deer, etc.) must travel long distances to find enough food b/c many plants have tough leaves with a waxy coating to reduce water loss

• Supports small population of larger predators like mountain lions and wolves

Ex.) California Chaparral

Temperate Grasslands

• Located in N. America, S. America, Europe, and Asia

• Tend to be located in the middle of the continent

• Continental climate

Continental Climate

• Hot summers, cold winters

• Long cold winters = relatively short growing season

• Growing season coincides with most of the year’s precipitation

– 300-1,000 mm per year

Precipitation

• Range in precipitation supports a variety of grass species

• N. America precipitation increases as we move east from the Rocky Mountains

• Shortgrass Prairies: Driest areas of the grassland

• As we move farther east grass gets taller tallgrass prarie

Fire

• Spreads quickly due to dry grass and strong winds

• Grasses survive fires by growing from areas at or below the soil surface

Animals

• Rich soil and lush grass support huge herds of grazers

– Bison

– Pronghorn

– White-tailed deer

• Animals consume up to 50% of NPP in grasslands compared to 5-10% in most other biomes

Prairie Dogs

• Live underground in large groups that are known as towns

• High density exerts heavy pressure on local plants has a positive effect

• Increases nitrogen content and digestibility of local plants while leaving total biomass unchanged

• Bison graze near prairie dog towns

Example: Great Plains of N. America

Temperate Forests

• Found in N. Cali, E. coast of N. America west to the Mississippi, Europe, Asia, and Australia

• Receive 650-3000 mm of precipitation/yr

• Most located between 40 and 50° N and S although some extend to 30°

Growing Season

• Have relatively short growing seasons

• Brevity of growing seasons is partially responsible for major characteristic: deciduousness

• Deciduous trees: drop their leaves (usually in the autumn) and re-grow new leaves the following spring

– Green for only part of the year

Deciduousness

• Shedding leaves costs a lot, but so does keeping leaves

– Must use energy to rebuild in spring, cannot photosynthesize without leaves

– Leaves require energy for maintenance always but in the winter or with age photosynthetic rate declines

• Just before dropping leaves plants withdraw ½ of the leaves N and 1/3 of the P

Payback Period

• The time it takes a leaf to capture an amount of energy equivalent to the amount of energy used to make the leaf

• Ex.) Japanese Elm

– Requires 9-15 days to generate the amount of energy required to produce them

• Ex.) Japanese Evergreen

– 30 days

Animals

• Must deal with short growing season

• Natural selection favors adaptations that allow animals to ride out the cold winter

• Hibernate during the winter and live off of stored energy

– Bats

– Bears

Migration

• Fly south toward the equator during the winter months

• Avoid the cold and lack of food

Detritivore Food Chain

• Leaves that trees drop provide much organic material for decomposers

– Earthworms

– Insects

– Fungi

• Without detritivores forest growth would slow because dead leaves and trees would “lock up” nutrients

Boreal Forests

• Grow at high latitudes 50-65° N

• Few people live in these areas

• Exist in N. America, Asia, and Europe as a more or less continuous belt around the Northern Hemisphere

• Growing season is usually shorter than 6 months

Climate

• 200-600 mm of precipitation per year

• There is enough water to support trees b/c the cold temperatures allow precipitation to exceed evaporation most of the year

• Marked by climatic extremes up to a 100°C temp difference between warmest and coldest days of the year

Shape and Activity

• Controlled by solar radiation, air temp, and availability of soil water

• Maximum day length varies between 16 and 24 hours

• Many tree species require long periods of sunlight to trigger their growing season

• Natural selection favors day length, not temp, to control growing cycles b/c temp is so variable

Plant Life

• Sun is never really overhead, tree canopies are shaped to absorb light at low angles

• Moisture is usually plentiful but roots cannot absorb water from frozen soil trees suffer water shortage

• Extreme environmental conditions cause most trees to be evergreen

Evergreens

• Leaves have very long life spans 25-30 years

• Keeping leaves over the winter requires little energy because the cold temps reduces maintenance respiration

• Cold temps slow decomposition which reduces nutrient availability in soils

• Specialization for water transport favors keeping leaves

Animals

• Caribou, reindeer, moose, wolves, Siberian tigers, grizzly bears, and many birds

• Many migrate or hibernate

• Those that are active year-round are often well insulated with fat, fur, or feathers

• Some fur and feathers turn white during winter for camouflage

• Feet and body shape adapted for the snow

Tundra

• Thin belt that stretches across N. America, Europe, and Asia – most of which is North of the Arctic Circle

• Precipitation ranges from 200-600 mm per year

• Temp. range is less extreme than the boreal forest

• Growing season is shorter than the boreal forest

Plants

• Covered with low-lying plants such as mosses, lichens, grasses, sedges, and members of the heath family

• Plants are covered by snow much of the year which allows them to avoid extreme winter temperatures

• No trees because of short growing season and permafrost

Permafrost

• Any soil material that remains below 0°C for two years or more

• Roots cannot extract frozen water from the soil

• Permafrost keeps rooting depth too shallow for trees

Rooting Depth

• The vertical distance from the soil surface that contains 95% of plant’s roots

Animals

• Animals living at high latitudes have smaller surface areas than their lower latitude relatives

• Ex.) Ears of arctic fox smaller than those of the red fox

– Shorter ears reduce amount of body heat lost

Body Size

• Small

– Allows them to spend winter under the snow which protects them from the temps

• Ex.) Lemming

– Can develop and mature more rapidly complete life cycles in the short growing season

• Large

– More exposed to the extreme conditions

• Ex.) Reindeer

Example: Alaska