L10.2 Desert Biome Flashcards
Where are deserts found
30˚ North and South of the equator
What are the climatic conditions in a desert
Temperature can vary but rainfall is always low
Arid
What are the soils like in deserts
Coarse with low water retention
What are the 2 types of desert
Tropical and temperate
What are the conditions in a tropical desert
High pressure and temperatures, intense solar radiation
Where are temperate deserts found
Lie in rain shadow of mountains or inland
What are the temperature conditions in a temperate desert in summer vs winter
High temp in summer
Below freezing in winter
What is the mean rainfall in deserts
300mm per year
What is the cloud cover like in deserts
Sparse
What is the name given to the way water breaks down rocks
Evapotranspiration
What is the landscape like in deserts
Uniform
What is the goal behind the great green wall of Africa
Planting trees into the Saharha to decrease desertification
How long have arid conditions existed
Since Devonian times, 420 MYA
How does desert flora relect its long evolutionary history
Richness and uniquness
Give an example od convergent evolution among desert flora
Cactaceae and Euphorbiaceae
No relation to eachother but experience same pressure
Where are Cactaceae found
In America’s
What are the areas of high biodiversity in savannas
Oases
What are the 3 predominant plant types in savannas
Therophyte annuals
Succulent
Non-succulent
What is growth like in therophyte annuals
Dormant for a long period then short quick growth
What are the 4 main adaptations for savanna plants
Drought escape
Drought evade
Drought endure
Drought resist
What is drought escape
Avoid drought by being in seed form until rainfall
Germinate and grow when moisture is available
What kind of plants use drought escape
Therophytes - short lived annual herbs occuring after rains, creat seasonality
What plants use the drought evade stratergy and how does it work
Perennials, non-succulents (grasses, shrubs, trees0
Growth only active in moist conditions, roots can lie dormant until rain occurs
Still exist at other times, just dont grow
Wha plants use the drought endure method
Mainly perennials
Non-succulent (shrubs and trees) with deeper root systems
What adaptations do drought evade plants have
(What are there roots and leaves like, what do they have in their cell wall)
High root:shoot ration
Shed leaves in dry season
Cell wall impregnated with waxy fars (prevent transpiration)
Varnish like coating over leaves
Thick hairy cuticles
Whay kind of plants use the drought resist stratergy
Succulents
What adaptations do drought resistant plants have
(Roots, stems, cell wall, leaves)
Shallow roots, lateral and thin
Swollen stems
Cell walls impregnated with waxy fats
Spines as leaves - reduce transpiration and reduces temperature
What type of photosynthesis do drought resistant plants use
CAM
Describe the root system of a tree vs a cactus
Tree: long complicated roots searching for more water
Cactus: horizontal roots, when it raisn it can collect water immediately
What happens in CAM photosynthesis and why do it
Carbon dioxide fixation at night
Reactions seperated in time
Lower temperatures at night reduce water loss
Stomata closed during day, no water loss
What is the point of the rib or accordion like structure of cacti
Allows for rapid volumetric expansion, serves as a mechanism to enhance water storage
Stretch without tearing plant tissue
Why do some succculents grow close ogether, give an example plant
Clustering creates microclimate, better for trapping moisture
Lithops
When do ephermal therophytes germinate
After sufficient rain
When do zerophytic shrubs grow
Can be active thoughout the year in seasonal deserts
Other plant adaptations to arid environments
Extensive lateral root systems
Reduced leaves or spines
Thick waxy xuticles
Leaf hairs
Regulation of leaf temp to maintain photosynthetic efficienct
Salt glands or sacraficial leaves
C4 photosynthesis
CAM photosynthesis
Give an example of plants with salt glands and ehy they have them
Salty soils
Chenopodiaceae
What plants use C4 photosynthesis
Halophytic shribs and perennial grasses
What pants use CAM photosynthesis
Succulents
How productive are deserts
Not very
Give an example of niche partitioning in deserts
Differential root systems
Where do annuals grow in deserts
In association with established perennials
What human activities can effect deserts
Urban encrochment
Irrigation
Agriculture
Settlement
Oil drilling
