lesson 5.1 evolution b. mechanisms of evolution · pdf file2 b. artificial selection lesson...

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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


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:


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


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


(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


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


• 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


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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


• 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:




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)




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


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 (+/–)


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(+/–)


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


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


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


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.


California Condor

Did You Know? Scavengers, such as vultures and condors, are just large detritivores.



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


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)




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)


• 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


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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


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


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


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


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


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.

lesson 5.1 evolution b. mechanisms of evolution · pdf file2 b. artificial selection lesson...

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