Lecture 5: Organisms: Convergent environmental adaptation & terrestrial biomes Flashcards
what is a biome
Geographic regions composed of organisms with similar adaptations.
how are biomes and convergent evolution connected
-ecosystems in the same biome in different parts of the earth show convergent evolution in animal and plant life
-Adaptation to geographic regions with distinct abiotic conditions drives convergence in biotic composition and ecological interactions
how do you define biomes by their charactersitics
they are characterized by the intersection of annual patterns of temperature and precipitation and the associated dominant plant cover
why do ecologists care about biomes
-provide large-scale comparisons of ecological processes across the globe
-Replication of organismal adaptation at the global scale
tropical rainforest biome - temperature and precipitation
-Temperature: stable, pretty high, never at 0 degrees Celsius (water doesn’t freeze)
-Precipitation: pretty high, some seasonal change (in earlier months of the year), never 0
tropical rainforest biome - soil and dominant plants
-Soils are old, shallow, and nutrient poor, due to high decomposition rates, nutrient loss, and nutrient uptake
-Tall forest trees dominate as a plant growth form - high species diversity
-Lianas and epiphytes grow on other plants to reach the canopy.
human impacts and the tropical rainforest
when human’s clear rainforests the land conversion exposes the landscape to extreme erosion from water
Tropical seasonal forest/savanna biome - temperature and precipitation
-Precipitation: there are months where rainfall is zero (the tropical ‘winter’), when wet – massive amounts of rainfall
-Temperature: high and stable, not as high as tropical rainforest, never freezing
tropical seasonal forest/savanna biome - soil and dominant plants
-Nutrient poor soils, similar to other tropical biomes.
-Dominant growth forms are grasses and low, broad trees.
tropical seasonal forest/savanna biome - how grasses and trees are balanced
- they are balanced through natural fires and grazing
-More frequent fires: more open
-Less fires: more closed, like a dry forest
tropical seasonal forest/savanna - what are rhizomes
fire and grazing adapted underground stems that allow rapid re-sprouting after damage
human impacts on the tropical seasonal forest/savanna biome
around Brazilian capital - a lot of land conversion for agriculture and settlement
Temperate seasonal forest biome - temperature and precipitation
-Precipitation: high in middle months
-Temperature: it is much lower than other forests, goes below zero (water freezes)
temperate seasonal forest biome - dominant plants
-North: broad leaf trees
-South: more diverse, more pine trees, soil becomes more sandy and loose
-both lose their leaves
-Understory layer of shrubs and smaller trees.
temperate seasonal forest biome - soil
Lower temperatures, and reduced growing season has led to deeper soils with abundant organic material — favors accumulation
temperate seasonal forest biome - why are there rivers and streams here
-Precipitation exceeds evaporation and transpiration
-water moves down through soils and drains via groundwater
human impacts on the temperate seasonal rainforest biome (UK)
-Europe has almost no old-growth forest left
-bc of hospitable environment there are massive land clearings for agriculture
human impacts on the temperate seasonal rainforest biome (US)
-Dramatic loss of old-growth forest cover (1620 - 1990)
- now: old-growth forests are coming back, especially in the Northeast
Temperate grassland/cold desert biome - temperature and precipitation
-moderate annual rainfall
-cold temperatures
Temperate grassland/cold desert biome - soil and dominant plants
-Grass is the dominant growth form in regions with higher rainfall and cooler summers
- low decomposition rates and nutrient rich soils
human impacts and the temperate grassland/cold desert biome
-Massive land conversion for food production, driven by the fertile soil, this effects the prairie environments
Subtropical desert biome - temperature and precipitation
-Almost no water. Water mainly comes in underground from nearby biomes
-rainfall is concentrated in the summer
-high summer temps, mild winters
subtropical desert biome - soil and dominant plants
-Often very shallow soils with almost no organic material accumulation.
-Creosote bush is the dominant growth form in drier regions of the biome
-Cacti and small trees become dominant in moister regions.
Woodland/scrublands - temperature and precipitation
-Temperatures: never freezing, stable (not super hot/cold)
-Precipitation: during warm periods – low water
-Hot, dry, summers and mild, wet winters
Woodlands/scrublands - soil and dominant plants
-Dominant vegetation is drought-tolerant grasses and shrubs.
-Deep roots and small durable leaves on the shrubs.
Human impact and woodlands/scrublands biome
-Lots of droughts and wildfires
-High human density and natural dry and fire-prone biome characteristics increases the chances of a human initiated wildfire
-Natural wildfire adaptions in plants are suppressed bc of human fire-preventions which then causes more destructive fires
