Transcript Edges of Life

Desert Life
Desert ecology
Desert ecology
• Why are deserts dry?
• What adaptations to animals and
plants need to live there?
Desert ecology
Deserts
• Definition of a desert: less than 10
inches of rain per year, more
evaporation than precipitation
• This is caused either by dry winds
(air heating up as it gets warmer), a
mountain “rainshadow”, or lack of
water in the middle of a continent
Desert ecology
Why are deserts dry?
• Rainshadow of mountain / middle of
continent
• Falling air / cool air holds little
moisture
– and at this latitude, air often falls
from having risen at the equator
Desert ecology
Deserts
Desert ecology
North American Deserts
• Sonoran
Desert
• Mojave Desert
• Chihuahuan
Desert
• Great Basin
Desert
Desert ecology
North American Deserts
Characteristic plants:
• Sonoran Desert: Saguaro, cacti
• Mojave Desert: Joshua tree
• Chihuahuan Desert: yuccas
• Great Basin Desert: sagebush
The abiotic environment
Why does any organism
live where it lives?
Usually three kinds of explanations:
• Abiotic environment (the right
climate, nesting sites, etc.)
• Biotic interactions (prey is there)
• History (it evolved there and did not
migrate somewhere else)
The abiotic environment
Why are most cacti only found
in the American deserts?
• Abiotic environment (dry with periodic
rain; not too cold)
• Biotic interactions (can defend
themselves against desert herbivores
and compete with other desert plants)
• History (evolved in the Americas, and
cannot migrate to Africa, for example)
Desert ecology
North American Deserts
Characteristic plants because of
characteristic climate:
• Sonoran Desert: winter and summer rains
(monsoon), very hot
• Mojave Desert: winter rains, hot
• Chihuahuan Desert: summer rains, warm
• Great Basin Desert: winter rains, high
elevation, colder (especially in winter)
Desert ecology
Desert adaptations
• Animals and plants that live in the
desert are adapted to the hot, dry
climate.
• Three basic methods:
– Evade
– Endure
– Expire
Desert ecology
Evade Endure Expire
• Migrate
away in
summer
• Only be
active at
night
• Minimize
water loss
• Maximize
heat loss
• Store
water
• Adults may die
before it gets
too hot
• Durable eggs
or seeds
survive to next
wet season
Desert ecology
Endure: ways to cope
with hot & dry climate
•
•
•
•
•
•
Store water
Conserve water
Tolerate dehydration
Reduce heat input
Dissipate heat
Tolerate hypothermia
Desert ecology
Endure: ways to cope
with hot & dry climate
•
•
•
•
•
•
Store water
Conserve water
Tolerate dehydration
Reduce heat input
Dissipate heat
Tolerate hypothermia
Desert ecology
Endure: ways to cope
with hot & dry climate
•
•
•
•
•
•
Store water
Conserve water
Tolerate dehydration
Reduce heat input
Dissipate heat
Tolerate hypothermia
Desert ecology
Endure: ways to cope
with hot & dry climate
•
•
•
•
•
•
Store water
Conserve water
Tolerate dehydration
Reduce heat input
Dissipate heat
Tolerate hypothermia
vertical leaves, insulation
with hairs
Desert ecology
Endure: ways to cope
with hot & dry climate
•
•
•
•
•
•
Store water
Conserve water
Tolerate dehydration
Reduce heat input
Dissipate heat
Tolerate hypothermia
Desert ecology
Endure: ways to cope
with hot & dry climate
•
•
•
•
•
•
Store water
Conserve water
Tolerate dehydration
Reduce heat input
Dissipate heat
Tolerate hypothermia
Summary
Deserts
• Deserts are drier than other places
• But there are different kinds of deserts
depending on the temperature, seasons,
and when & how much rain
• Animals and plants are adapted to a
particular “niche”, which includes climate
and other species
• Where an animal/plant lives also has
historic reasons