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5Evolution and Community EcologyC
HA
PT
ER Black and White, and Spread
All Over
• Zebra mussels and quagga mussels were accidentally introduced into Lake St. Clair in the late 1980s.
• They have since spread throughout the Great Lakes system and connecting rivers.
• The invasive mussels have a high economic and ecological cost.
Talk About It The Great Lakes are home to more than
20 native mussel species. Why are the zebra and
quagga mussels so much more destructive than the
lakes’ native mussels?
Lesson 5.1 Evolution
Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered.
a. Evolution and Natural Selection
• Evolution: change over time
• i. Over time, changes occur in the gene pool. .. All the genes present in a population
• ii. Gene: A sequence of DNA that codes for a particular trait
Lesson 5.1 Evolution
A starting population of dogs.
Genes control the color and
pattern of the dogs’ coats.
b. Mechanisms of Evolution:
i. Mutations
Lesson 5.1 Evolution
changes in DNA
that can give rise to
variation among
individuals; can be
good changes (such
as stripes or no
stripes in fish) or
harmful
Mechanisms of Evolution:
Lesson 5.1 Evolution
ii. Migration (gene flow)
A change in the
proportion of
organisms with a
certain trait due to
moving away of one
group
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Mechanisms of Evolution
Lesson 5.1 Evolution
iii. Genetic Drift
iv. Natural Selection
Evolution that occurs by “chance”:
Natural disasters can result in
change in population density and
type
Propagation of traits that enhance an organisms survival; the strongest organisms will survive, passing on best traits.
II. Natural Selectiona. Conditions of Natural Selection
Lesson 5.1 Evolution
(1) Organisms
produce more
offspring than can
survive.
(2) Individuals vary in
characteristics, some
of which are heritable.
(3) Individuals vary in
fitness, or reproductive
success; this is reflected
in their habitat
II. Natural Selectiona. Conditions of Natural Selection
Lesson 5.1 Evolution
1. Fitness – how
reproductively successful
and organism is.
2. Adaptations – trait that
increases an organisms
ability to survive
iv. Survival of the fittest – the most fit animal will produce
more offspring and pass on genes more frequently than
ones of lower fitness
b. Artificial Selection
Lesson 5.1 Evolution
• i. Process of selection (of traits) based on human
intervention.
• ii. Animals – many varieties
of dogs, which can all
interbreed. Varieties are
maintained by selective
breeding.
• iii. Plants – artificial selection gives
us most of the food we eat today;
one plant gives rise to many more.
• iv. Allows us to select the traits we
like the most
c. Speciation
Lesson 5.1 Evolution
QuickTime™ and a
decompressor
are needed to see this picture.
• Process by which
new species are
generated/created
• Can occur in a
number of different
ways; the most
important way is
called allopatric
speciation: separation
for long periods of
timeAllopatric Speciation
d. Extinction – disappearance
Lesson 5.1 Evolution
• i. 99% of all species that
have ever lived are extinct
• ii. Fossil record shows
species lasting 1-10 mill. yr
• Generally occurs when
conditions change more
rapidly than the species
can adapt (background ext)
• There are five worldwide
mass extinction events,
each of which wiped out a
large proportion of Earth’s
species. (Genesis Flood)
Did You Know? During the Permo-Triassic
extinction 250 million years ago, 70% of all
land species and 90% of all marine species
went extinct.
Trilobites
Marine arthropods that went extinct at
the end of the Permian period.
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Lesson 5.2 Species Interactions
The zebra mussel has completely displaced 20 native mussel species in Lake St. Clair.
1. The Niche
Lesson 5.2 Species Interactions
• A. Habitat is the general place an organism lives.
• B. Niche includes where it live, eats, reproduces and
interacts with others.
• C. Tolerance –
• i- An organism’s ability to survive and reproduce under
changing environmental conditions
• Specialists have narrow range of tolerance (pandas)
• Generalists have a wide range (rats)
d. Competition• Organisms compete when
they seek the same limited resource.
• In rare cases, one species can entirely exclude another from using resources.
• To reduce competition, species often partition resources, which can lead to character displacement.
Lesson 5.2 Species Interactions
QuickTime™ and a
decompressor
are needed to see this picture.
Resource Partitioning
Predation (+/–)
• The process by which a predator hunts, kills, and consumes prey
• Causes cycles in predatory and prey population sizes
• Defensive traits such as camouflage, mimicry, and warning coloration have evolved in response to predator-prey interactions.
• Some predator-prey relationships are examples of coevolution, the process by which two species evolve in response to changes in each other.
Lesson 5.2 Species Interactions
Did You Know? A single rough-skinned newt contains enough poison to kill 100 people. Unfortunately for the newt, its predator, the common garter snake, has coevolved resistance to the toxin.
Rough-Skinned Newt
Parasitism and Herbivory (+/–)
Lesson 5.2 Species Interactions
Did You Know? One study of Pacific estuaries suggests that parasites play an important role in keeping these ecosystems healthy by controlling host populations.
Hookworm (a parasite)
• Parasitism: One
organism (the parasite)
relies on another (the
host) for nourishment or
for some other benefit
• Herbivory: An animal
feeding on a plant
Mutualism (+/+) and Commensalism (+/0)
Lesson 5.2 Species Interactions
Did You Know? Symbiosis describes a long-lasting and physically close relationship between species in which at least one species benefits.
• Mutualism: a
relationship in which two
or more species benefit
• Commensalism: a
relationship in which one
species benefits while
the other is unaffectedLichen: a symbiotic relationship
between a fungus and a photosynthetic
partner, such as an alga
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Lesson 5.3 Ecological Communities
The sun provides the energy for almost all of the ecological communities and species interactions on Earth.
A. Primary Producers (Autotrophs)i. Energy cannot be created or
destroyed (1st Law of Thermodynamics)
ii. Plants capture energy from sun or chemicals and store it as sugar
• 1. Energy (light) from sun is the main source for photosynthesis:
• 6CO2 + 6H2O + energy = C6H12O6 + 6O2
Lesson 5.3 Ecological Communities
Did You Know? Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis.
Primary Producers (Autotrophs)• 2. Chemosynthesis - Energy
from chemicals when no light is available, converts hydrogen sulfide instead of light:
• 6CO2 + 6H2O + 3H2S = C6H12O6 + 3H2SO4
3. Both methods use carbon dioxide and water to make sugar
Lesson 5.3 Ecological Communities
Did You Know? Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis.
B. Consumers (Heterotrophs)
i. Organisms that rely on other organisms for energy (like us)
ii. Use the sugar from photosynthesis (food) for energy
iii. Use oxygen to release energy from sugar: cellular respiration :
iv. 6CO2 + C6H12O6 = 6CO6 + 6H2O
Lesson 5.3 Ecological Communities
California Condor
Did You Know? Scavengers, such as vultures and condors, are just large detritivores.
B. Types of Consumers
i. Herbivores – primary consumers that eat producers(plants)
ii. Carnivores – eat other animals
iii. Omnivores – eat both plants and animals
iv. Detrivores – eat only non-living (dead) organisms
• V. Decomposers – breakdown dead plants/animals so plants can use them as nutrients and the cycle starts over again.
Lesson 5.3 Ecological Communities
California Condor
Did You Know? Scavengers, such as vultures and condors, are just large detritivores.
QuickTime™ and a
decompressor
are needed to see this picture.
II. Energy and Biomassa. Trophic Levels – pyramid
model show ranking in feeding hierarchy
b. Energy
i. Entropy – Energy tends to move from order to disorder (2nd Law of Thermodynamics);
ii. Example of tank of gas: only about 14% gets used, rest is lost as heat
iii. Organisms use energy from food but burn it in the process
iv. Only 10% of energy is available for each succeeding trophic level
Lesson 5.3 Ecological Communities
Pyramid of Energy
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Biomass in Communities
c. Total amount of living tissue (plant or animal) at each trophic level
• i. Each level has less mass because of less available energy
Lesson 5.3 Ecological Communities
QuickTime™ and a
decompressor
are needed to see this picture.
Food Chains and Webs
a. Food Chain – a linear series of feeding relationships that shows energy transfer
b. Food Web – more realistic model of how organisms feed on each other, because animals usually eat more than one type of food
Lesson 5.3 Ecological Communities
•where one organism has big effect on whole ecosystem; without that one species, the whole system falls apart (example of sea otters)
Keystone Species
Lesson 5.3 Ecological CommunitiesLesson 5.4 Community Stability
A 2010 report on invasive species suggests that they cost the U.S. $120 billion a year in environmental losses and damages.
Invasive kudzu
1. Ecological Disturbances
Lesson 5.4 Community Stability
• A. A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity.
• B. Disturbances or changesin the environment can throw a community into disequilibrium.
• C. Severe disturbances can cause permanent changes to a community and initiate a predictable series of changes called succession.
Forest fire
2. Primary Succession
Lesson 5.4 Community Stability
a. Occurs when there are no traces of the original community remaining, including vegetation and soil.
b. Pioneer species, such as lichens, are the first to colonize.
c. The environment changes as new species move in, adding nutrients and generating habitat.
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3. Secondary Succession
Lesson 5.4 Community Stability
a. Occurs when a disturbance dramatically alters a community but does not completely destroy it
b. Common after disturbances such as fire, logging, or farming
c. Occurs significantly faster than primary succession
4. Succession in Water
Lesson 5.4 Community Stability
a. Primary aquatic succession occurs when an area fills with water for the first time.
b. Disturbances such as floods or excess nutrient runoff can lead to secondary aquaticsuccession.
i. Algae add nutrients
ii. Debris builds on bottom
iii. Lake fills in, becomes a meadow
5. Climax Communities
Lesson 5.4 Community Stability
a. Ecologists once thought succession leads to stable“climax” communities.
b. Today, ecologists see communities as temporary, ever-changing associationsof species.
c. Communities are influenced by many factors and constant disturbances.
Beech-maple forest, a classic “climax community”
6. Invasive Species
Lesson 5.4 Community Stability
a. Nonnative organisms that spread widely in a community
b. A lack of limiting factors such as predators,
parasites, or competitors enables their population to
grow unchecked.
i. Zebra mussel
ii. Cane toad
iii. kudzu
c. Not all invasive species are harmful.
Did You Know? Although the European
honeybee is invasive to North America, it is
beneficial because it pollinates our agricultural
crops.