Download Chapter 4

Chapter 4

Ecosystems and Living Organisms
Evolution

A process of change through
time
Theory of Evolution
1.
2.
Suggests that existing forms of life
on earth have evolved from earlier
life forms over long periods of time
Evolution accounts for the
differences in structures, function,
and behavior among life forms as
well as changes that occur in
populations over many generations
Charles Darwin
Darwin


Charles Darwin devised a theory of evolution
based on variation and natural selection as seen
in the Galapagos islands.
Included in his theory were five main ideas:
1. Overpopulation
2. Competition
3. Survival of the fittest/Natural selection
4. Reproduction
5. Speciation
1. Overpopulation

Within a population, there are
more offspring produced in
each generation than can
possibly survive
2. Competition
Natural resources; like food, water,
and space available to a population
is limited
 Because there are many organisms
with similar nutritional
requirements, there must be
competion between them for the
resources needed to survive

3. Survival of the Fittest
Variations
among members of a population make some of
them better adapted to the environment than others
It
is generally the best-adapted individuals that will
survive
The
environment is the agent of natural selection
determining which species will survive.
Survival of the Fittest
Survival of the Fittest
Survival of the Fittest
Natural Selection
1.
2.
3.
4.
Natural selection involves the struggle of organisms to
survive and reproduce in a given environment
Traits which are beneficial to the survival of an
organism in a particular environment tend to be
retained and passed on, and therefore, increase in
frequency within a population
Traits which have low survival value to an organism
tend to decrease in frequency from generation to
generation
If environmental conditions change, traits that have
low survival value may now have a greater survival
value. Therefore, traits that prove to be favorable
under new environmental conditions will increase in
frequency
Ex: Insects resistant to insecticides
Genetic make-up of some insects make them resistant
to the effects of insecticides
2.
Before the widespread use of insecticides, this trait was
of no particular survival value
3.
With the increased use of insecticides, this trait
developed a very high survival value
4.
Therefore, insects with resistance to insecticides
survived and reproduced much more successfully than
those lacking the trait
5.
As a result, the frequency of insecticide resistance has
increased greatly in insect populations
Important! The trait already exists within the genetic makeup of the organism.
1.
4. Reproduction
Individuals that survive and
then reproduce, transmit these
variations to their offspring

5. Speciation
The development of a new species
occurs as variations or adaptations
accumulate in a population over
many generations
 Ex: caveman  present man

Speciation: “Bigfoot? Sasquatch?
Evidence which supports the
Theory of Evolution
1. Fossil record
2. Comparative anatomy of organisms
3. Biogeography (Study of species distribution)
4. Molecular Similarities
Diversity and classification
The 5 Major Kingdoms
1.
2.
3.
4.
5.
Monera-(Bacteria)
Protista
Fungi
Plant
Animal
Six Kingdom Taxonomic System
Rotting Log Community:
An Ecosystem
Ecosystem Formation Ecosystems
tend to change over a
long period of time until a stable
ecosystem is formed.
 Both the living and nonliving parts
of an ecosystem change.
(A) Ecological Succession
The replacement of one kind of community with
another is called ecological succession.
 The kind of stable ecosystem that develops in a
particular geographical area depends on climate.
 Pioneer organisms- are the first plants to
populate an area. Lichens and algae may be
pioneer organisms on bare rock. (Create soil)
 Climax Communities- Succession ends with the
development of a climax community in which the
populations of plants and animals exist in balance
with each other and the environment.

Ecological Succession
Secondary Succession

When a previously inhabited environment is
disturbed, and must undergo a new round of
succession.

Examples- Mt. St. Helens,Yellowstone fires
Keystone species


These determine the
nature and structure of
an entire ecosystem.
Usually found in
small numbers but
have a key influence.
Examples:
Wolves, Fig Trees
Coevolution
Interdependent
evolution of two
species
Results in symbiotic relationships
Coevolution
Symbiosis
An intimate relationship
between two or more species
Mutualism
 (+
, +)
 In this relationship both organisms
benefit from each other.
 Ex: Anenome and clown fish
Mutualism
Commensalism
(+ , o)
 One
benefits, one not affected
 Epiphytes (mosses, orchids, ferns) attach
themselves to tree bark and obtain their
nutrients without harm to the trees.
Parasitism
 (+
,-)
 One helped, one harmed
 Pathogens (disease causing agents)
are parasite that harm a host
organism.
 Crown gall disease in plants., TICKS
Predation


Predators exert strong selective
pressures upon their prey.
Both prey and predator evolve in an
attempt to be more successful and
survive.
Predator/Prey Relationships
Data collected from fur pelts from the Hudson Bay Company
Studies have shown that Endocrine changes
in populations may produce behavioral
changes which tend to limit population
growth. Therefore all population changes
may not be due to predator/prey relationships
alone.
Defensive Adaptations in Animals
Chemical defenses: Sprays, stinging cells
 Warning Coloration: avoidance of predators by
unpalatable animals. Ex: Poison Dart Frog.

Defensive Adaptations in Animals
Cryptic coloration (Camouflage): Blending into the
surroundings for avoidance of predators by
palatable animals.
 Ex: Argentinean Horned Frog
Defensive Adaptations in
Animals
Mimicry: resemblance to another species.
 Ex: Io moth, Monarch and Viceroy
butterflies
Competition
1.
Different species living in the same
environment, or habitat, may require the same
resources. When the resources are limited,
competition occurs among the species.
2.
Intraspecific: competition within a population
Interspecific: competition between species
Competition
2.Competition- is the struggle between different
species for the same limited resources. The
more similar the needs of the species, the more
intense the competition.
Competition
3.Each species occupies a specific niche in the
community. A niche is the role the species plays,
and includes the type of food it eats, where it
lives, where it reproduces, and its relationships
with other species.
Limiting Factors
Are
those resources that are scarce!
Cause population size to be limited.
Results in resource partitioning and
competitive exclusion.
Resource Partitioning: differences in
resource use among species.
Limiting Factors Gause’s Experiments
Limiting Factors Gause’s Experiments
Which type of Competition?
Interspecific Competition!
Competitive Exclusion: one species is
excluded from a portion of a niche by another
as a result of interspecific competition.
(Two species with identical niches can’t coexist.)
Species Richness
Related to the # of available niches
 Tropical rain forests- Most diversity/Low #’s
 Mountaintops/Tundra- Low diversity/High #’s
 More stressful habitats have lower diversity.

Community complexity and species diversity