Lecture 13 (chapter 11) Flashcards
Environmental variation
- In spite of their
variation, ecologists
have classification
schemes aggregate
ecological variation into
clusters with general
similarity of structure
and function of the organisms found there
What is a biome?
Bioms are: Clusters of ecosystems that have a general similarity in structure of the ecosystem
Where do they exist: Over an
extensive geographic
range, occurring
anywhere in the world
that environmental
conditions are suitable
- Biology of biomes is defined by climate
- We characterize biomes
by late-successional
vegetation and
characteristic animals
4 main biomes=
boreal forest:
Temperate grasslands
Tropical rainforest
- Not the particular species that are preset that defines them but the way the environment looks (morphological) or the dominant organisms of the area
Biomes are demined by climate
- Abiotic factors influence biomes
- Temperature on x-axis (goes hot to cold)
- Y axis = precipitation
- end up with a triangular distribution
- low precipitation in cold
- higher participation in warm
- warm and wet = tropical rain forest
warm and less wet tropical seasonal forest
desert
temperate forest is middle
tiger and tempera cold dry
Why do different parts of the world have different biomes?
- Biomes are defined by temperature
- earth is tilted at a 23 degree angle
the fact that it is tillted give rise to percipatation regimes and temperatures
Winter solstice:
Sun directly overhead
(90°) at Tropic of
Capricorn at midday
- vernal equinox:
Sun directly
overhead (90°) at
equator at midday
Summer solstice :
Sun directly overhead
(90°) at Tropic of
Cancer at midday
Autumnal equinox:
Sun directly overhead
(90°) at equator at
midday
Annual variation in day length corresponds with distance from the equator
- Warm air at the equator rises-cools - water molecules condense and it’ll rain
- This is why we have a tone of rain by the equator
- the air continues to rise past the rain clouds cools and shift back down to the earth 30 degrees south or north
- this precipitation gives rise to rain forests
Global distribution of deserts results from the
return of dry air near 30ºN and 30ºS
general climatic and precipitation
patterns at different latitudes
equator- apple percipitation
summer wet /winter dry
dry all seasons
wiinterwet summer dry
apple percipitation all seasons
sparse precipitation all year
Tundra
- High latitude biome
- Growing season too short to support trees
- dominate vegetation grasses lichen moses
not enough growth season for large vegetation - Low precipitation, low evapotranspiration
- Permafrost (layer of peet that can be frozen year round) prevents drainage
- Small shrubs, grasses, and sedges
ex.
Dominant large herbivore
in arctic tundra is
migratory caribou
Very short window of opportunity to breed there but still allows many
migratory birds to breed
in the arctic
Low biodiversity
Temperate zone
- Lies north of the topic of cancer south of capercorn
Temperate zones lie
between the Arctic /
Antarctic and the Tropics
of Cancer / Capricorn - Variable vegetation,
depending on latitude
and the pattern of
precipitation - Marked seasonal
variation is
commonplace
Boreal forest (taiga) look at figure 11.5
Dominated by coniferous
trees
* Spread across the
Northern Hemisphere
* Short but warm
summers
* Deciduous trees such as
aspen and birch after
disturbance such as fire
Temperate deciduous forest
- Cold short winters
- Summer warm and long
enough to support many
deciduous trees - In Canada, highest tree
diversity is in southern
Carolinean forests - High species richness is
common in southern
temperate deciduous
forest - lots diversity
Fall leaf coloration Why do we see this as a colourful and defining feature of this biome?
Yellow and orange colours in fall leaves are
carotenoids, unmasked by the breakdown of
chlorophyll
* The red colours are
anthocyanins, newly
produced in the fall as
protection (produced deliberately at this time)
* These colours are not a
incidental product of leaf
senescence
- Resorbing helpful nutrients from leaves to center of tree
Why are our forests so colourful?
** Read why does fall foliage turn so
red and fiery? It depends. New York
Times**
All leaf colour
* Photoprotection
hypothesis: red pigments
protect against the
harmful effects of light at
low temperatures
(protective pigment)
- Coevolution hypothesis:
red is a warning signal
toward insects migrating
to the trees in autumn
(warning symbol to bugs to try and stop them from laying their eggs on them
Temperate rainforest
Found only in western North America (only where rainfall if most abundant)
* Bountiful precipitation all year
* Mild winters (not quite as much snow as temperate disdace forest)
* Highest conifer diversity of all biomes
* Abundant moss epiphyte (plants growing on other plants)
Rain forest
At least 2 m of rainfall
Temperate grassland
Low annual precipitation
* Insufficient moisture to support forests
* Cold winters, hot
summers
* Fire and herbivores (bison) keep trees out in
the more humid regions (tallgrass prairie)
- Herbivores eat any of the big growth.
Chaparral
ex. California
Mild, moist winters; hot dry summers; a
“Mediterranean climate”
* Poor soils and fires limit tree growth
* Dominant plants are shrubs
* Fires are a key part of
chaparral system, but fire
prevention has meant
accumulation of fuel,
threatening this biome
Deserts
- Too dry for vegetation
- Deserts occur in tropical,
temperate, and even arctic
climates - Plants show strategies to
tolerate arid climate: - Storing water
(succulents) - Avoiding dry periods
(annuals) - Having deep roots
- Cam photosynthesis stmi closed during day open at night
Tropical savanna and dry forest (fig 11.11)
Tropical climate with a dry season
* Long drought: savanna
(grassland) with
scattered trees
* Fire and large herbivores
limit tree growth in
savannas
* Short drought: dry
forests with deciduous
trees
- earth’s most endangered biome
- easy to turn into pastureland
Evergreen tropical rainforest
No dry season
* No frost
- Daily temperature change= annual temperature change
- Close to equator
* Diurnal temperature
fluctuations are larger
than seasonal
fluctuations
* Often daily precipitation
* High productivity and
biomass
* Complex vertical
structure
FIGURE 11.12
Lentic ecosystems
What is it: Lakes and ponds with
standing (non-flowing)
water
* Characteristics are shape
and volume, nutrient
concentration, water
transparency
* Distinct habitats
* Littoral (shore)
- Pelagic (open water)
- Benthic (bottom)
Eutrophic vs oligotrophic ecosystems
Nutrient concentration
in lakes determines
productivity
* Eutrophic: nutrient rich (Lake Erie)
* Oligotrophic: nutrient
poor (fewer nutrients, ex.Lake Superior)
Lotic ecosystems
- Flowing water: rivers,
streams - Key characteristics:
amount, speed, seasonal variation, and turbidity of water (how many nutrients) - Primary productivity often not self-sustaining:
consumers supported by upstream lakes or
terrestrial ecosystems - can have seasonal pulses
Freshwater wetlands: Define bogs, swamps, marshes
Characteristics determined by water nutrient content and variation in water level
* Bogs: low productivity with no
inflowing groundwater; very acidic can walk on it (no open water)
* Fens: mineral rich with inflowing groundwater; non-acidic (still have inflowing groundwater)
* Swamps: fertile wetlands dominated by trees or shrubs (can have seasonal flooding- not always wet)
* Marshes: fertile wetland dominated by grasses
Marine biomes: open ocean
Currents and upwellings
determine ecological
variation in open ocean
* Low productivity per unit
area
* Pelagic: currents and
upwellings cause
variation
* Benthic: mostly
heterotrophic
open ocean
Hydrothermal vents at
ocean bottom show
diverse life at high
temperatures and
pressures, based on
primary production by
chemosynthetic bacteria
Marine biomes: continental shelf
More productive than
open ocean
* Nutrients from rivers or
upwellings
* Seashores: ecology
determined by bottom
characteristics
* Estuaries: productive
regions at
marine/freshwater
interface
* Coral reefs: ecosystems
built by animals
Anthropogenic ecosystems
Ecological characteristics
convergent in different
climate zones
* Can be centuries old
* Often with adapted
organisms
* Three clusters:
– Urban
– Rural
– Agroecosystems
Most ecosystems in inhabited
areas are more or less
influenced by humans.
Urban ecosystems
Can have relatively high
biodiversity due to
heterogeneity, warm
microclimate, and
species introductions
through humans
* Many species are alien,
do not survive without
human influence
Rural ecosystems
Extensive networks of
highways, railroads,
electrical lines,
industrial facilities, and
towns associated with
the harvest and
processing of natural
resources
Agroecosystems
Modern agricultural
practices can lead to
unstable ecosystems
with low diversity
* Centuries-old low-
intensity agricultural
practices may have
resulted in high species
diversity (e.g. European
hay meadows)
