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APES
Unit 03
Chapter 6
Ecosystems and
Ecosystem
Management
Basic Characteristics
of Ecosystems
•
•
Sustained life on Earth is a characteristic of
ecosystems, not of individual organisms or
populations
Structure (two major parts)
– Living (Ecological Communities)
– Non-living
•
Processes (two basic kinds)
– Cycling of chemical elements
– Flow of energy
•
Change
– Predictable – succession
– Unpredictable change
Ecological Communities
and Food Chains
• Ecological Communities are
defined in two ways:
– 1. A set of interacting
species that occur in the
same place defined by the
way they derive energy: Food
chains, food webs, trophic
levels (autotrophs)
– 2. A set of all species found
in one area. EG. Zoo animals
Food Chains
and Food Webs
• A Terrestrial Food Chain
– Four trophic levels:
– Example:
•
•
•
•
Autotrophs
Herbivores
Carnivores
Decomposers
– People are omnivores
Food Chains and
Food Webs Continued…
• An Oceanic Food Chain
– Involve more species and tend to
have more tropic levels. See figure
6.6
• The Food Web of the Harp Seal
– Shows how complex a real-life food
web truly is.
The Community Effect
•
•
Species interact directly (symbiosis &
competition) and indirectly
Community-level interactions
– Indirect interactions.
•
Keystone species
– Have large effects on it’s community or
ecosystem
– Its removal changes the basic nature of the
community
– See Sea Otter example figure 6.8. Sea otters
influence the abundance of sea urchins
•
Holistic View
– An ecological community is more than the sum
of its parts.
How Do You Know When You
Have Found an Ecosystem?
• Vary greatly in structural
complexity.
• The watershed is a
common, practical
delineation.
• What is a watershed?
• Common to all ecosystems
is energy flow and cycling
of chemical elements.
Ecosystem Management
• Ecosystem management is the key to
conservation of life on Earth, but it is difficult
to know the exact limits of the system and is
equally difficult to know all of the interactions
that take place within it.
• If ecosystems cease to function we must
supplement with our own actions.
• Must consider chemical cycling, energy flow,
community-level interactions, and natural
changes.
Chapter 7
Biological
Diversity
Biological Diversity
and Biological Evolution
• Biological Diversity (biodiversity)
– The variety of life-forms commonly
expressed as the number of species in an
area
• Biological Evolution
– The change in inherited characteristics of
a population from generation to generation
– One of the features that distinguishes life
from everything else in the universe
Four Processes that
Lead to Evolution
•
•
•
•
Mutation
Natural Selection
Migration
Genetic Shift
Mutation
• A chemical change in a DNA molecule
• Affects the expressed characteristics
when cells or individual organisms
reproduce
Natural Selection
• 4 Characteristics:
–
–
–
–
Genetic Variability
Environmental Variability
Differential Reproduction
Environmental Influence
• Species:
– a group of individuals that
reproduce with each other
and produce fertile offspring
Peppered Moth Example
• Originally White
• Now more black than white
• Causes
– Industrial Pollution
• Soot covered trees
– Industrial Melanism
http://www.echalk.co.uk/Science/science.htm
Migration
• Two new species evolve
from an original species
due to isolation
• Ex: land bridge
Genetic Drift
• Changes in the
frequency of a gene in a
population due to
chance
• Can be a problem for
rare or endangered
species
Basic Concepts of
Biological Diversity
•
•
•
•
•
•
Genetic Diversity
Habitat Diversity
Species Diversity
Species Richness
Species Evenness
Species Dominance
Species
•
•
A group of organisms that can reproduce and
produce fertile offspring.
Ubiquitous species
– Worldwide distribution
– Overly common in an area
•
Endemic species
– Organisms unique to one place only.
•
Indicator species
– The first native organisms in an ecosystem, to
show the effects of environmental problems.
The Number of
Species of Life on Earth
• No one knows the exact
number
• About 1.4 million species
have been identified and
named
• Insects and plants make up
moth of these species
• Number will increase
The Competitive
Exclusion Principles
• 2 species that have exactly
the same requirements
cannot coexist in exactly
the same habitat
• Ex) introduction of the gray
squirrel into Great Britain
Professions and Places: The
Ecological Niche and the Habitat
• Habitat: where a species
lives
• Ecological Niche: a species
profession
• The reason more species
do not die out from
competition is that they
have developed a niche,
and thus avoid competition
What is the
effect of each
species on
the other?
Species Engage in
3 Basic Interactions
• 1. Competition
• 2. Symbiosis
• 3. Predation-Parasitism
• Each affect evolution, persistence of a
species and the overall diversity of life
• Organisms have evolved together and
therefore adjusted to one another
• Human interventions upset these
adjustments
Symbiosis
• The relationship between two
organisms that is beneficial to both
and enhances each organisms
chances of persisting
– Mutualism, parasitism, commensalism
• Obligate symbionts:
– a symbiotic relationship between two
organisms in which neither by themselves
can exist without the other
– Ex) stomach of a reindeer
Chapter 8
Biogeography
Part I
Why Were Introductions of New Species
into Europe So Popular Long Ago?
• Biogeography:
– The large scale
geographic pattern in the
distribution of species,
and the causes and
history of this distribution
Wallace’s Realms:
Biotic Provinces
•
Realm:
– Major biogeographic regions of Earth that
are based upon fundamental features of the
plants and animals found in those regions
•
Taxa:
– Categories that identify groups of living
organisms based upon evolutionary
relationships or similarity of characteristics
(ex: species, families, orders)
•
Biotic Provinces:
– A geographical region (realm) inhabited by a
characteristic set of taxa, bounded by
barriers that prevent the spread of those
distinctive kinds of life to other regions.
The main biogeographic realms for animals are based on
genetic factors .
The major vegetation realms are also based on genetic factors
Biomes
• A biome is a kind of ecosystem. Similar
environments provide similar opportunities
for life and similar constraints.
– Rainforest
– Grasslands
– Desserts
Climate is the most
important factor in
determining the type of
biome that will be found in
an area
Convergent Evolution
• The process by which species
evolve in different places of
times and, although they have
different genetic heritages,
develop similar external forms
and structures as a result of
adaptation to similar
environments
– Ex) shapes of sharks
Divergent Evolution
• Organisms with the same
ancestral genetic heritage
migrate to different habitats
and evolve into species with
different external forms and
structures, but continue to
use the same type of
habitats
– Ex) Ostrich
Island
Biogeography
• Theory of Island Biogeography
– Islands have fewer species than continents
– The smaller the island, the fewer the species
• Adaptive Radiation:
– The process that occurs when a species
enters a new habitat that has unoccupied
niches and evolves into a group of new
species, each adapted to one of these
niches.
• Ecological Island:
– An area that is biologically isolated so that a
species occurring within the area rarely
mixes with any other population of the same
species
1. Islands far
from the
mainland tend
to have a lower
rate of
immigration
2. Small
islands
have
higher
rates of
extinction.
Which island would have the largest population based on 1 & 2?
Islands
have fewer
species
than the
mainland.
This is a
product of
size as is
seen on
this graph.