Biomes: Where Do Plants and Animals Live? animals with similar life forms and environmental...

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Transcript of Biomes: Where Do Plants and Animals Live? animals with similar life forms and environmental...

  • 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


    – 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