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