Transcript Chp. 6: “Ecosystems and Evolution”

Chapter 6
Ecosystems in the
Environment
The Tall Grass Prairie
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Biodiversity is high
Deep rich soils
Home to over 200
plant species
Habitat for variety of
wildlife
The Tall Grass Prairie
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In Canada, tall grass prairie used to
stretch out across 6,000 sq kilometers in
MB and 1,200 sq kilometers in ON
Today, it is the rarest ecosystem in
Canada
What can be done to conserve Tall grass
prairie ecosystems?
Biomes
Large, distinct terrestrial regions
 Climate is a determining factor
 Elevation also
important
 Nine major
biomes
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Earth’s Terrestrial Biomes
Tundra
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Extreme northern latitudes
Alpine tundra: high elevations
Short growing season
Nutrient-poor soils
Treeless
Permafrost
Limited precipitation
Tundra
Relatively few species
 Mosses, lichens, grasses, sedges
 Lemmings, arctic
foxes, weasels,
snowy owls, caribou
 Mosquitoes,
black flies, deerflies
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Boreal Forest
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Northern coniferous
forest
Just south of tundra
Cold, extreme winters
Little precipitation
Some permafrost
Acidic, mineral-poor
soil
Boreal Forest
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Coniferous trees: why?
Caribou, wolves, bears, moose
Rodents, rabbits, mink, lynx
Abundant birds in summer
Temperate Rain Forest
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NW North America, SE Australia,
Southern S. America
Lots of precipitation
Mild winters, cool
summers
Nutrient-poor soil
Temperate Rain Forest
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Large evergreen trees
Epiphytes
 Plants growing on trees
 Mosses, ferns, lichens
Squirrels, elk, birds, amphibians, reptiles
Temperate Deciduous Forest
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SE Canada
Rich topsoil, clay
beneath
Fair amount of
precipitation
Dense canopy of trees
Much of it was logged
and cleared
Temperate Deciduous Forest
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Originally: cougars, wolves, bison
Deer, bears, many birds
Today used for recreation, livestock,
timber harvest
Case Study: Ontario’s
Carolinian Forest
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Forest extends from
Carolinas in US to SW ON
Close to 80% has been lost
Close to 40% of the
species on Canada’s
endangered and
threatened species list live
in the Carolinian Forest
What can be done?
Temperate Grassland
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Prairies of Canada;
today, agriculture
Hot summers, cold
winters, uncertain
precipitation
Mineral-rich, thick
topsoil
Periodic wildfires
Temperate Grassland
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Grasses, wild flowers, some trees
Formally, herds of bison, elk
Wolves, coyotes, prairie dogs, grouse,
reptiles, insects
Tropical Rain Forest
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Central & South America, Africa, SE Asia
Warm temperatures,
a lot of rain
Ancient, mineral-poor
soil
Species rich
Tropical Rain Forest
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Three stories
 Topmost: emergent
layer
 Middle: canopy
 Bottom: understory
Most species in the
canopy
Insects, reptiles,
amphibians, birds,
mammals
Chaparral
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Southern California
mountaintops
Mediterranean
climate
Abundant rain, dry
summer
Thin, infertile soil
Chaparral
Dense evergreen shrubs
 Fire-adapted
plants
 Mule deer,
wood rats,
lizards, birds
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Savanna
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Africa, S. America,
India, N. Australia
Intense seasonal
rainfall
Prolonged dry
periods
Little temperature
variation
Soil low in nutrients
Savanna
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Grasses, occasional trees
Large herds: wildebeest, antelope, giraffe,
elephant
Lions, hyenas
Desert
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Dry areas, major
temperature change in
24 hours
Temperate,
subtropical, tropical
Soil low in organic
material, salty
Desert
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Sparse plant cover
Cacti, yuccas, Joshua trees
Animals usually small
Tarantulas, scorpions, reptiles, kangaroo
rats, owls
Aquatic Ecosystems
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Freshwater and saltwater
environments
Three types of organisms
 Plankton: small, drift
 Nekton: swim; fish,
whales
 Benthos: bottom
dwellers
Major Marine Life Zones
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Marine environment is subdivided into
several zones
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Intertidal zone: area of shoreline between
low and high tides
Benthic environment: ocean floor
The two provinces: neritic (from shore to
where water reaches a depth of 200 meters)
and oceanic (water depth greater than 200
meters)
Coral Reefs
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Formed over thousands of generations
Found in warm shallow water where
light penetrates
Most diverse of all
environments
Provide habitat
and prevent
shoreline erosion
Sea Grasses
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Extensive beds of sea grass occur in
temperate, subtropical, and tropical waters
Have high primary productivity
Roots and rhizomes
stabilize sediment,
reduce erosion and
provide food and
habitat
Kelp Forest
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Photosynthetic, primary food producers,
and provide habitat
Standing-Water Ecosystems
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Lakes, ponds
Three zones
 Littoral: shallow, along shore
 Limnetic: open water; extends down to
where sunlight penetrates
 Profundal: deepest; no light penetration
Thermal stratification
Three Zones
Flowing-Water Ecosystems
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Rivers, streams
Highly variable
Flooding
Some areas shaded,
others not
Organisms vary
depending on
current
Flowing-Water Ecosystems
Freshwater Wetlands
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Marshes, swamps: difference?
Waterlogged soils
Waterfowl,
other birds
Beaver, otters,
fish
Ecosystem
services
Estuaries
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Coastal body of water
Partly surrounded by land
Access to open ocean and fresh water
Water levels rise and fall
Salinity fluctuates
Organisms must adapt to daily, seasonal
changes
Estuaries: Salt Marshes
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Temperate
regions
Salt-tolerant
grasses
Ecosystem
services
Estuaries: Mangrove Forests
Tropical regions
 Ecosystem services
 Important for commercial fish and shellfish
 Nesting sites
for many birds
 Prevent coastal
erosion
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Evolution
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Change over time
Characteristics & organisms
Populations evolve (not individuals)
Natural selection
 Mechanism of evolution
 Charles Darwin
Natural Selection
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Tendency for better-adapted individuals
to survive and reproduce
Four main ideas
1) Overproduction
2) Variation
3) Struggle for
survival
4) Differential
reproductive success
Darwin’s
Finches
Fossil Record
Fossils deposited in rock layers, which can be dated,
show how organisms evolved over time. These fish
fossils from Liaoning Province, China, date from 120
million years ago.
Comparative Anatomy
Similarities among organisms demonstrate how they are
related. These similarities among four vertebrate limbs
illustrate that, while proportions of bones have changed in
relation to each organism’s way of life, the forelimbs have the
same basic bone structure.
Molecular Biology
The organisms pictured here all
share a particular enzyme, but
in the course of evolution,
mutations have resulted in
changes in the gene that codes
for that enzyme. This diagram
shows the nucleotide base
differences in this gene among
humans and other organisms.
Note that organisms thought to
be more closely related to
humans have fewer differences
than organisms that are more
distantly related to humans.
Succession
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Gradual change in plant species
composition in a given area
Ecologists formerly believed in a climax
community: stable and persistent
Communities are in a constant state of
disturbance
Measured in tens, hundreds, or thousands
of years
Primary Succession
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Occurs in uninhabited area
Start with nothing
Bare rock
Pioneer communities move in
Soil formation
Lichens  mosses  grasses  shrubs 
trees
Primary Succession
Secondary Succession
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Start with something (reestablish)
Area degraded
Abandoned farm field, burned forest
Faster than primary succession
Secondary Succession
Intermediate Disturbance
Hypothesis
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Disturbances can determine which species
are able to live in a habitat
Intermediate Disturbance Hypothesis
attempts to predict changes in species
abundance and diversity at changing
disturbance levels
The capacity of an organism to cope is
known as ecosystem resilience
Eco Canada Career Focus
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Consider a career as
an Environmental
Manager
Work to ensure that
proposed projects
have as little
environmental
impact as possible
Case Study: Boreal Forest
Fires
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Essential disturbance factor
Started by lightning, humans
Destroys old diseased trees and pests, restarts plant succession
Leftover ashes are rich in nutrients
Soil left exposed  germination of seeds
Increased soil erosion
Many grasses and trees adapted to fire
Case Study: Boreal Forest
Fires
Humans suppressed fire  fuel
accumulates
 Now, when a fire
occurs it is hotter,
more destructive
 Prescribed burning
helps
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