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