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 DesertsCharacteristic 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 DesertsCharacteristic 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
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