Lecture 4 Flashcards
______ vary with mean annual temperature and precipitation
biomes
High biomass, high
diversity—about 50% of
Earth’s species
Warm temp (seasonally invariant), lots of precipitation
biome is characterized by broad-leaved evergreen and deciduous trees
light is a key environmental factor determining vegetation
tropical rainforests
fire is important in maintaining diversity
toward Tropics of Capricorn (S) and Cancer (N)
rainfall more seasonal (wet and dry seasons)
vegetation response - shorter stature, low tree densities, increasing degree of drought deciduousness, with leaves dropping from trees during the dry season
used to cover area greater than Tropical Rainforests but have resulted in rates of loss due to increasing human demand for supplies of wood a agricultural land
less than half of this biome remains intact
tropical seasonal forests and savannas
grassland with sparsely populated trees
savanna
not a lot of precipitation
sparse vegetation and animal populations BUT still diverse (just not abundant)
convergence —-> plants with succulent stems can store water in their tissue (i.e. agave, cacti)
periods of high temps and low water availabilities, high rates of evapotranspiration
generally correspond to descending air of Hadley cells
hot deserts
greater seasonal precipitation and temperature
usually associated with warm, moist summers and cold, dry winters
soils are particularly well suited for agricultural development
temperate grasslands
precipitation not in sync with temperature (seasonal)
winter rainy seasons (Mediterranean-type climates)
fire is important for regulation
temperate shrublands and woodlands
agricultural development in these areas are dependent upon irrigation
often use water from ____
flows in from distant mountains or extracted from deep underground
irrigated agriculture in deserts has repeatedly failed due to
salinization (58)
long-term droughts in association with unsustainable grazing practices can result in loss of plant cover and soil erosion
this process is known as
desertification
_____ leaves are a solution to extended period of freezing weather in temperate zone
temperate deciduous forests
often along the coast (Cali, Australia)
precipitation varies substantially among these forests
generally lower diversity
subjected to extensive clearing; little-old growth forests remains
commonly on nutrient-poor soils (related in part to acidic nature of the leaves of the trees)
temperate evergreen forests
subsurface soil layer that remains frozen year-round for at least 3 years in boreal forests
permafrost
severity of winters increases
a lot of collected litter (lacks moisture and fungal activity in for example, a rainforest)
i.e. Scandinavia, Alaska, Siberia
boreal forests
low growing-season temperatures
low nutrient, low solar radiation
shrubs
tundra
mountain biological zones
lower montane zone, montane zone, subalpine zone, alpine zone
freshwater biological zones
associated with:
velocity, depth, temp., clarity, and chemistry of water
spatial zonation of a stream
main channel –> swimming organisms live in flowing water
benthic zone —> insect larvae and crustaceans on the stream bed
hyporheic zone –> rotifers, copepods, and insects live in the substratum
descending water converges into progressively larger stream and rivers
flowing water
lotic ecosystems
lakes and still water; occur where natural depressions have filled with water or where humans have dammed rivers to form reservoirs
lentic ecosystems
marine biological zones
determined by ocean depth, light availability (degree of light penetration)
\_\_\_\_\_\_ allow plants to be active during cooler, wetter periods. Sclerophyllous leaves—tough and leathery—deter herbivores and prevent wilting.
Evergreen leaves
lotic ecosystems
first order: source streams at the highest elevation
second-order streams: two first-order streams join to form these
third-order streams: two second order streams join
lake biotic assemblages associated with depth and light penetration
open water - pelagic zone
open water - pelagic zone in habited by plankton
photic zone - photosynthetic plankton aka phytoplankton (where there is enough like for photosynthesis)
littoral zone - nearshore zone where the photic szone reaches to the lake bottom (Macrophytes occur in this zone)
Lakes can be formed by
glacial processes,
from river oxbows, in volcanic craters, in
tectonic basins, or by animal activities,
including humans and beavers
marine biological zones
intertidal zone
coral reefs
intertidal zone - barnacles, starfish with adaptations to changing conditions
coral reefs - HIGH diversity of life (but losing bc temp and pollution)
Organisms in the pelagic zone include:
Nekton (swimming organisms capable of
overcoming ocean currents)—fish,
mammals, sea turtles, squid, octopus.
Phytoplankton—green algae, diatoms,
dinoflagellates, and cyanobacteria.
Zooplankton—protists (e.g., ciliates),
crustaceans (e.g., copepods and krill),
and jellyfishes.
Ocean bottoms (benthic zone) are
No light
sparsely populated, with temperatures
near freezing, and very high pressure.
