Transcript An Introduction to Ecology and the Biosphere

Ecology is the study of the interactions
between organisms and their
environments.
 In this chapter – we will focus on:
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1. The scope of ecology
2. Factors affecting the distribution of
organisms
3. Aquatic and terrestrial biomes
4. The spatial scale of distributions
Abiotic: nonliving environmental factors
Biotic: living environmental factors
Ecological time: minutes/months/years
Evolutionary time: decades/centuries, etc.
Population: group of individuals of the same
species living in a particular area
 Community: all organisms of all species that
inhabit a particular area
 Ecosystem: all biotic and abiotic factors
that exist in an area
 Biosphere: the global ecosystem – sum of
entire planet’s ecosystems
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Biogeography: the study of past and
present distribution of individual species.
Figure 50.4 –
continental drift and
barriers such as
deserts and mountain
ranges all contribute
to the distinctive floras
and faunas found in
Earth’s major regions.
1.
Species Dispersal
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2.
3.
4.
Species transplants
Introduced species
Behavior & Habitat Selection
Biotic Factors
Abiotic Factors
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Dispersal: the distribution of individuals
within geographical population
boundaries.
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Question: Is the distribution of a species
limited by dispersal (i.e. by movement
of the organisms)?
› Answer can be obtained by transplant
experiments.
 If the transplant is successful, then the
organisms just haven’t reached the target
area.
 If the transplant is not successful, then
other factors limit the distribution of the
organisms, such as competitors, lack of a
food source, etc.
Figure 50.6
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Humans have moved species around the globe!
› Can be deliberate or accidental – but BOTH can be
BAD!
› Example: African Honey Bee (pg. 1097)
› Example: Zebra Mussel (pg. 1097)
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Why do invaders succeed?
› New habitat with no natural predators, often unlimited
food supply – potential for rapid population growth.
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What’s the harm of the invasion?
› out compete native species – disrupt food webs/chains,
change ecosystems, kill native species, difficult to control
(Kudzu)…the list goes on and on!!!
Not all introduced species thrive in their
new environment – many fail to colonize.
 The Tens Rule makes the statistical
prediction that an average of one out of
ten introduced species become
established
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› And…one out of ten established species
become common enough to become pests.
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Organisms may not occupy all
potentially suitable habitats. Why?
› Evolution doesn’t lead to perfect organisms.
› Evolution is an ongoing process.
Environments change, but it takes a while for
organisms to respond.
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Organisms that are required for potential
community members to colonize may be
lacking:
› Pollinators, prey, predators that limit
competition, etc.
Figure 50.9 –
Researchers test effects
of 2 herbivores (sea
urchins & limpets) on
the abundance of
seaweeds.
Both present (red) – no
algal cover.
Predator-removal
demonstrates that sea
urchins are main
herbivores limiting
distribution of the
seaweeds.
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Temperature
› Especially for ectotherms
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Water
› All living things need water for survival (some
more than others)
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Sunlight
› Light intensity limits plant growth!
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Wind
› Increases heat loss & water loss
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Rocks & Soil
Figure 50.10 – The
areas plotted here
encompass the
range of annual
mean temperature
and precipitation
occurring in the
biomes.

Climate & Biomes:
Climate – prevailing
weather conditions at
a locality.
Microclimate –
climate locally
varying on a small
scale (i.e. on a forest
floor or under a rock).
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Ponds & lakes are sensitive to seasonal
temperature changes
› During summer & winter, many lakes in
temperate regions are thermally stratified
(layered vertically according to temperature).
› Such lakes undergo biannual mixing of their
waters as a result of changing water temp.
profiles (called turnover).
› Turnover brings oxygenated water from surface
of lakes to bottom and nutrient rich water from
bottom of lake to top
 These events are essential for survival and growth
of organisms at all levels within the ecosystem!
Wetlands
 Lakes
 Rivers, streams
 Intertidal zones
 Oceanic pelagic biome
 Coral reefs
 Benthos
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Photic Zone – upper zone; light sufficient for
photosynthesis
Aphotic zone – lower zone; little light penetrates
Water temperature also stratified
› Colder water is deeper
› Oceans (some lakes) have thermocline (narrow layer that
separates the two types of water)
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Benthic zone – bottom of all aquatic biomes – sand
and inorganic sediments
› Organisms that live here are called benthos
› Benthos survive on detritus
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Standing bodies (lakes, ponds)
Moving bodies (rivers, streams)
Littoral Zone – regions occupied by floating and
rooted plants; shallow water close to shoreline
Limnetic zone – open waters away from shore;
occupied by phytoplankton, zooplankton, fish, etc.
Profundal zone – aphotic zone where detritus
accumulates
Lakes classified according to production of organic
matter
› Oligotrophic lakes – deep and nutrient-poor, sparse
phytoplankton; clearer water
› Eutrophic lakes – shallower, nutrient rich, productive
phytoplankton; murky waters result
› Mesotrophic – inbetween
Oligotrophic Lake: Nutrient poor, water is clear,
oxygen rich; little productivity by algae, relatively
deep with little surface area.
Eutrophic lake: nutrient rich, lots of algal
productivity so it’s oxygen poor at times, water
is murkier  often a result of input of
agricultural fertilizers
Rivers and Streams: Organisms need adaptations
so that they are not swept away by moving water;
heavily affected by man changing the course of
flow (E.g. dams and channel-straightening) and by
using rivers to dispose of waste.
Wetlands: includes marshes, bogs, swamps, seasonal ponds. Among richest
biomes with respect to biodiversity and productivity. Very few now exist as they
are thought of often as wastelands. Favor growth of water plants and also rich in
invertebrates and birds.
Estuary: Place where freshwater stream or river merges with the ocean. Highly
productive biome; important for fisheries and feeding places for water fowl.
Often heavily polluted from river input so many fisheries are now lost. Salt
marsh grasses, algae, phytoplankton, many invertebrates.
Marine environment with zonation.
Intertidal Zone: Alternately submerged and
exposed by daily cycle of tides. Often
polluted by oil that decreases biodiversity.
Coral Reefs: occur in neritic zones of
warm, tropical water, dominated by
cnidarians (corals); very productive,
protect land from storms; most are
now dying from rise in global
temperatures
Neritic zones are shallow regions over
continental shelves – beyond
intertidal zone.
Deep-sea vent: Occurs in benthic zone; diverse, unusual organisms; energy
comes not from light but from chemicals released from the magma.
Tropical rainforest
 Savannah
 Desert
 Chaparral
 Temperate grassland
 Temperate deciduous forest
 Coniferous forest
 Tundra
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Tropical Forest
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Pronounced vertical stratification
Canopy trees make up most o f the upper stratum; little light reaching ground
Rainfall is major determining factor in types of plant growth
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Large herbivores and predators
Many insects
Grasses and scattered trees
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sparse rainfall
temperature varies – cold at night, hot during day
animals and plants adapted to dry climate
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dense, spiny evergreen shrubs
mild rainy winters, long hot summers
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prairies of N. Amer. are example
grasses, herbivores
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Deciduous trees
Sufficient moisture to support tree growth
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Cone bearing trees
Pacific NW
Taiga – Northern Coniferous forests; heavy snowfall during winter
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Permafrost
absence of trees
little annual rainfall
high winds and cold temperatures
Savanna
Desert
Chaparral
Temperate Grassland
Temperate Deciduous Forest
Coniferous Forest
Tundra