Lecture 3.1 / 3.2

What are biomes?

Large geographic regions with similar climate, distinct abiotic conditions and dominant vegetation types

Describe abiotic?

Non-living

• temperature

• water

• sunlight

• soil

• wind

Describe biotic?

Living

• plants

• animals

• microbes

• interactions

What are the abiotic and biotic characteristics of Tundra?

Abiotic

• very cold

• low precipitation

• permafrost (frozen soil)

• high winds

Biotic

• no trees

• small shrubs, mosses, lichens

• low diversity + productivity

What are the abiotic and biotic characteristics of Taiga?

Abiotic:

• cold, long winters

• wet, acidic soils (bogs)

Biotic:

• coniferous trees (pine, spruce)

• low biodiversity

• animals adapted to cold

What are the abiotic and biotic characteristics of a Temperate Deciduous Forest?

Abiotic

• moderate temperature

• consistent precipitation

• rich soils

Biotic

• broad-leaf trees (oak, maple)

• leaves fall in winter

• medium biodiversity

What are the abiotic and biotic characteristics of a Temperate Grassland?

Abiotic

• dry to moderate rainfall

• fires common

• fertile soil

Biotic

• grasses dominate

• few trees

• large herbivores

What are the abiotic and biotic characteristics of a Desert?

Abiotic

• extremely dry (≤ 25 cm rain/year)

• hot or cold

• poor soil

Biotic:

• low plant diversity

• many animals (rodents, reptiles)

• drought-adapted plants

What are the abiotic and biotic characteristics of a Chaparral?

Abiotic

• hot, dry summers

• mild, wet winters

• fire-prone

Biotic

• shrubs, small trees

• fire-adapted plants

What are the abiotic and biotic characteristics of a Savanna?

Abiotic

• warm year-round

• seasonal rainfall

Biotic

• grasses + scattered trees

• large animals (elephants, lions)

What are the abiotic and biotic characteristics of a Tropical Rainforest?

Abiotic

• warm + very wet year-round

• near the equator

Biotic

• extremely high biodiversity

• dense vegetation

• many layers (canopy, understory)

What are Hadley cells?

Large-scale air circulation patterns near the equator

How are Hadley cells related to desert biome distribution and conditions of tropical wet forests?

• warm air rises at the equator

• air cools → rain (tropical forests )

• air moves outward and sinks at ~30° latitude

• dry air = deserts

What are deserts?

Defined by lack of water, NOT temperature

What is a rain shadow desert?

Dry region

• moist air hits mountains

• rains on one side

• dry air descends on the other side

What are the North American deserts?

• Great Basin Desert

• Mojave Desert

• Sonoran Desert

• Chihuahuan Desert

What are the Great Basin Desert's respective indicator plant species?

• indicator plant: big sagebrush

• no cacti

What are the Mojave Desert's respective indicator plant species?

Indicator plant: joshua tree

What are the Sonoran Desert's respective indicator plant species?

Indicator plant: saguaro cactus

What are the Chihuahuan Desert's respective indicator plant species?

Indicator plant: agave lechuguilla

How are plants adapted for life in the Boreal forest?

• needle-like leaves → reduce water loss

• evergreen → photosynthesize year-round

• thick bark → cold protection

How are plants adapted for life in the Temperate Deciduous?

• drop leaves in winter → avoid freezing damage

• broad leaves → maximize sunlight

How are plants adapted for life in the Tropical Rainforests?

• large leaves → capture light

• drip tips → remove excess water

• shallow roots → absorb nutrients quickly

Explain how and why species abundance in biomes differs based on latitude?

Highest near the equator and decreases toward the poles because there are more species near the equator.

What percentage of all trees in the world are found in the Taiga?

30%

What are 2 ways coniferous trees are adapted to survive in the taiga?

Needle-like leaves

• Reduce water loss and prevent freezing damage

• Tough and not very appealing to herbivores

Waxy coating + evergreen habit

• Protects against cold and drying winds

• Leaves are hard to digest → helps avoid being eaten

How do coniferous trees avoid being eaten?

Leaves are hard to digest → helps avoid being eaten

What was the feeding strategy used by wolverines living in the Taiga?

They feed on carcasses (dead animals); they are scavengers

What do wolverines rely on?

• Strong sense of smell

• Ability to travel long distances to find food

How are the trees in the temperate deciduous forest different from those in the Taiga (Boreal Forest)?

• Taiga trees (conifers):

  • Needle-like leaves

  • Evergreen

  • Adapted to cold, dry, nutrient-poor conditions

• Temperate deciduous trees:

  • Broad leaves

  • Shed leaves in winter

  • Adapted to moderate temperatures and consistent rainfall

What is a likely evolutionary benefit of mass emergence as seen with the 17-year cicada?

Predator satiation