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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
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 Selection
a. 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 Selection
a. 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
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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
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i. Creation of new
species results by
separation of
species for long
periods of time
Allopatric Speciation
d. Extinction – disappearance of a species
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
• Occurs usually when
environmental conditions
change too quickly
(background extinction)
• Five worldwide mass
extinctions over time
(Genesis Flood is major
one)
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.
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 (-/-)
i. Results when multiple organisms seek the same resources
ii. How they compete produces different outcomes:
Lesson 5.2 Species Interactions
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Resource Partitioning
d. Competition (-/-)
1. Competitive exclusion principle – one organism lives, the other dies off as a result of being a weaker variety
2. Fundamental vs realized niche – species change behavior and start overlapping areas
3. Resource partitioning – change of behavior results in new niche and sharing of resources
4. Character displacement - species “evolve changes” that suit their environment and available resources (this the Darwinian model: organisms cannot change at will to suit their environment)
Lesson 5.2 Species Interactions
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Resource Partitioning
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II. Predation (+/–)
• Predation – process in which an organism hunts (predator) and kills another (prey)
i. Causes changes in population cycles
ii. Darwinian evolution says that both predator and prey can change/adapt for protection
iii. Creation model says that God created each species with the adaptations already there
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
b. Parasitism (+/–)
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)
i. Parasite depends on
its host for
nourishment; host is
usually harmed
ii. Symbiosis – a
relationship between
two organisms in
which at least one
benefits
c. Herbivory(+/–)
Lesson 5.2 Species Interactions
Rabbits and grass
i. Relationship between
animal and plant exist
together
ii.Plants do not die but are
affected by animal
feeding on it
III. Mutualism and Commensalism
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.
a. Mutualism (+/+): a
relationship in which two
or more species benefit
(symbiosis)
i. Bees pollinate flowers
ii. Mycorrhizae – fungus
gets nutrients to the
plant, plant give
fungus energy to grow
b. Commensalism: one
species benefits while the
other is not harmed
Lichen: a symbiotic relationship
between a fungus and a photosynthetic
partner, such as an alga
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.
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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. 6O2 + 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.
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II. Energy and Biomass a. 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
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 (lowest level has highest mass)
Lesson 5.3 Ecological Communities
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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 (therefore much competition results)
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 : if the sea otters didn’t eat the urchins, the urchins would eat all the kelp, then they and all other animals would die)
Keystone Species
Lesson 5.3 Ecological Communities
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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 changes in 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 (just rock)
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.
d. Can take hundreds of years to get to a climax community
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 aquatic succession.
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 associations of 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.