Evolution and Ecosystems

Chapters 4 and 5

Evolution by Natural Selection

1859, Charles Darwin proposed an answer to the question, “how do organisms become so well suited for their environment?” The answer he proposed is

Evolution by Natural Selection

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Evolution by Natural Selection Darwin noticed that in a population (same

species living in same place) the organisms are slightly different in: Form- how the body is shaped/colored

Small beaks vs. Large beaks Function- what the body does

Eating small seeds vs. Eating large seeds Behavior- what the organism does

Ignoring humans vs. Running away

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Evolution by Natural Selection Natural Selection

“Survival of the Fittest” In a certain environment, certain traits will help

an organism survive These organisms will have more offspring The next generation will have more traits that are

like those organisms Over time the population will evolve, so that the

traits that help survival will be found in more organisms

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Evolution by Natural Selection Darwin’s theory can be summarized in 5 steps:

Organisms produce more offspring than can survive The environment is hostile and has limited

resources Organisms differ in the traits they have Some traits provide an advantage Each generation will have more organisms with

advantageous traits The traits that helps an organism survive are

known as adaptations

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Evolution by Natural Selection

After several generations, most of the deer have thick fur.

Deer live in a warm climate and some have thicker fur than the others

Some deer get separated from the group

They end up in cold mountains, the deer with thicker fur are more likely to survive and have offspring.

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Evolution by Natural Selection Sometimes different organisms evolve to help

each other out This is called coevolution Insects get food by eating the nectar inside

flowers The have long straws that help them do this

The flowers give off pollen, which attached to the insect When the insect go to another flower it pollinates the

new flower

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Evolution by Artificial Selection Since the agricultural revolution we have

been domesticating animals and crops We breed animals so they have the traits we need

them to have Horses = speed/strength cows = quality of meat Dogs = beauty

Crops are breed to grow faster, bigger, be disease resistance, different colors, …

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Evolution by Artificial Selection This type of selective breeding that is

controlled by humans is called Artificial Selection

The Chihuahua is a descendent of the grey wolf

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Evolution of Resistance

In our quest to control nature we spray pesticides to kill insects

Unfortunately we have used pesticides, so much that insects have become resistant An organism can tolerate a chemical that is

designed to kill it

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Evolution of Resistance

Insects are sprayed with an insecticide.

Very few survive.

The survivors have offspring

They inherit the resistance

The same insecticide is used and many more survive and reproduce

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Genetics

Around the same time as Darwin, an Austrian monk, Mendel, was studying pea plants

He was trying to understand how different traits are passed from parents to children

Mendel breed different types of pea plants together and observed the flower color and type of peas

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Genetics

Mendel came up with 3 conclusions: There are different forms of the units that control

traits (flower color, pea type, eye color, …) For each trait there are 2 units, 1 from each

parent If the units are different, then 1 of them is

dominant and the other is recessive

We have found out since then that the “unit” is a gene

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Genetics

In order to keep a population healthy, there must be genetic variation Members of a population with different traits

(eye color, thick/thin fur, small/large beaks, …) This variation comes in 2 major ways:

Mutation Genetic Recombination

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Genetics- Mutation

A change in the gene of an organism that can be passed to its offspring is a mutation

Mutations that effect a single gene can do cause a range of damages These are typically not even noticed If they are noticeable then they are usually severe

and cause serious damage Mutations that effect multiple genes usually

result in the death of the organism

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Genetics- Genetic Recombination Genetic Recombination occurs when

organisms reproduce sexually Genes from 2 organisms combine to create an

offspring There are approximately 8 million unique genetic

combinations in humans

If an organism reproduces asexually, then the genetics are exactly the same as the parent Without mutations the population would not evolve

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Genetics- Evolution

If you look at evolution using genetics, then evolution can be defined as a change in gene frequency in a population Which genes are the most/least common

Remember: Individuals do not evolve, populations evolve.

The beauty of Natural Selection is in its simplicity It does not require any certain direction or end result It is only guided by random mutations in DNA

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Ecosystems Ecosystem

All organisms living in an area together with their physical environment

All plants, animals, rocks, water, and everything else All living and nonliving things! All ecosystems are connected!

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Ecosystems

All ecosystems need 5 things to survive: Energy Mineral Nutrients Water Oxygen Living Organisms

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Ecosystems

Biotic Factors Organisms (the living things) and stuff that came

from organisms Plants, animals, leaves, bodily waste

Abiotic Factors The nonliving part of the ecosystem Air, water, sand, rocks, light, temperature

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Ecosystems

Organism An individual living thing You, me, that bug on your shoulder!

Species Group of organisms that are closely related and

can mate to produce fertile offspring

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Ecosystems

Population All members of the same species that live in the

same place at the same time. Members of 1 population will usually breed with

each other rather than with other populations You wouldn’t fly to Austria just to find someone to marry

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Ecosystems Community

Various species that live in the same place and interact with each other

A Pond Plants, fish, insects, animals that live around the pond

You can belong to more than one community Birds that migrate during the seasons

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Ecosystems

Habitat The place where an organism lives Cactus = desert Waterlily = pond Salamander = damp forest floor

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The Kingdoms of Life

Organisms are classified based on their characteristics.

Six kingdoms: Archarbacteria Eubacteria Fungi Protists Plants Animals

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Bacteria

Bacteria Single cell, no cell

nuclei, and reproduce by dividing in half

Archaebacteria Live in harsh

environments Methanogens and

thermophiles Eubacteria

Extremely common Proteobacteria and

cyanobacteria

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Bacteria

Uses in the environment Break down waste and remains Recycle minerals (nitrogen and phosphorous) Convert nitrogen from the air into a form used by

plants Helps to digest food

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Fungi

Fungus Organisms whose cells

have nuclei, cell walls, and no chlorophyll

Absorb food through their body

Live mostly on land Mushrooms, molds,

mildews

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Fungi

Uses in the environment Break down dead organisms Add flavor to food Makes bread rise (yeast)

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Protists

Protists Wide range of organism

from single to many-cells. Usually live in water

Diatoms, algae, seaweed, phytoplankton, Plasmodium

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Protists

Uses in the environment Base of the food chain for most fresh and ocean

water ecosystems

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Plants

Plants Many-celled organism that make their own food

using the sun’s energy and have cell walls Lower plants, gymnosperms, angiosperms

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Plants- Lower

Lower Plants No roots Do not grow very big Lived in damp places Ferns and mosses

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Plants- Gymnosperms

Gymnosperms Woody plants whose seeds are

not enclosed in fruits Found in much dryer places than

Lower Plants Conifers (produces cones) Produce pollen and seeds Pine trees Responsible for most of the

lumber and paper

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Plants- Angiosperms

Angiosperms Flowering plants that produce seeds in fruit Produce pollen Rely on animals to carry pollen and seeds Most of the food we eat, oak trees and cotton

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Animals

Animals Many cells, no cell walls,

ingest food, live on land and in water

Much more mobile than plants

Move around in at least 1 stage of their lives

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Animals- Invertebrates

Invertebrates Animals without backbones Many live in the ocean attached to a hard surface Some move around only when they are larvae

Coral, mollusks, worms Other are active all of their lives

Squid, insects

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Animals- Vertebrates

Vertebrates Animals with backbones Fish, amphibians, birds, mammals, reptiles The 1st vertebrates were fish

Most now live on land The 1st land vertebrates were reptiles

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Energy flow

All life on Earth depends on sunlight As sunlight enters the ecosystem it drives

photosynthesis Which uses the light to make sugar

6 CO2 + 6 H2O + sunlight C6H12O6 + 6 O2

Carbon Dioxide Water Sugar

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Energy Flow

Organisms that use photosynthesis are known as producers They make their own food Autotrophs (self-feeder) Producers make-up the bottom of the food chain

Producers are then eaten by consumers Get energy by eating others Heterotrophs (other-feeder)

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Energy Flow

There's 1 exception to the need of sunlight: 1977 scientists make it to the bottom of the ocean They find that there is a ton of life at the very

bottom Since there is no light, how do they get energy

Plants use hydrogen sulfide coming out of the hydrothermal vents

This is extremely toxic to all of the rest of life on Earth

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Energy Flow

There are 4 types of consumers: Herbivore

Eats producers Vegetarians, cows, sheep, deer

Carnivore Eats other consumers Meatarians, lions, hawks, snakes

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Energy Flow

Omnivore Eats both producers and consumers Most humans, bears, pigs

Decomposer Breaks down dead organisms Fungi, bacteria

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Energy Flow

Producers use the sun's energy to create food

When consumers eat they use the food to create energy using cellular respiration This is the opposite of photosynthesis

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

Sugar Carbon Dioxide

Sugar Water

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Energy Flow

When a consumer eats another organism, it gains energy

The simplest sequence showing the transfer of energy is represented in a Food Chain

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Energy Flow

While Food Chains are nice, ecosystems are not simple Many things rely on the

same organism to survive

A more accurate representation of the transfer of energy is a Food Web

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Energy Flow

Each time energy is transferred in an ecosystem, the energy moves up a Trophic Level

90% of all energy at a trophic level goes to keeping the organism alive

The other 10% is stored and can be transferred up to the next level

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Energy Flow

Think of the energy loss like a pyramid These are all different Trophic Levels

The “Producers” Level has 1000 times the amount of energy than is at the Top of the pyramid

More Energy = More Organisms

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Cycling of Materials

• The Carbon Cycle– Movement of carbon from the environment to

organisms and back– Carbon atoms make up the basic structure of

ALL organisms

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Cycling of Materials

• Producers pull in CO2 from the atmosphere or

the water (marine life) during photosynthesis– It is turned into sugars and stored (becomes part of

the organism)

• Consumers then gain carbon atoms when they eat the producers– The carbon atoms are stored until cellular respiration– During cellular respiration carbon is released back

into the atmosphere

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Cycling of Materials

• When organisms die the carbon is released into the soil– If conditions are right, after millions of years this

carbon will become fossil fuels (coal, oil, natural gas)

• Human are currently digging up as much fossil fuel as possible to burn for energy– When fossil fuels are burned it releases CO2

• However, we are not putting the carbon back into the ground as fast as we are taking it out– This leads to global warming

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Cycling of Materials

• The Nitrogen Cycle– The movement of nitrogen from the environment

to organisms and back– All organisms must have nitrogen create proteins

and new cells

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Cycling of Materials

• 78% of the air is nitrogen– However, most organisms (including humans)

cannot use the nitrogen that is in the air– We must rely on nitrogen-fixing bacteria to convert

the nitrogen into a form we can use• This bacteria lives in the roots of bean and pea plants

– Once the nitrogen is “fixed” it is stored in producers • And is transferred to consumers when they are eaten

– When an organism dies the nitrogen is then returned to the soil

• Where other bacteria turn it back into nitrogen gas

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Cycling of Materials

• The Phosphorus Cycle– Movement of phosphorus from the environment

to organisms and back– This is a very slow cycle, and usually doesn't

involve the air

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Cycling of Materials

• Phosphorus is need by all organisms to create new cells

• This cycle starts with rocks that contain phosphorus

– As the rocks erode, small amounts of phosphorus go into the soil and water

– Plants will take in phosphorus from the soil• And Consumers take it in by eating the producers

– Once in the water it will sink to the bottom• This sediment will turn into new rock formations

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Cycling of Materials

• Nitrogen and Phosphorus are the 2 most important ingredients in fertilizers

• When we use fertilizers, some of it is washed away before plants can use it

• When it enters the water algae starts to grow

– So much grows that it creates a thick layer of green muck on top of the lake

• The algae grows so much that it takes up all of the oxygen from the water and kills all of the organisms

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How Ecosystems Change

Ecological Succession A gradual change in the types of species in a

community 2 types: Primary and Secondary

Primary Succession Occurs on a surface where an ecosystem has

never existed Rocks/cliffs, parking lots, volcanic islands

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How Ecosystems Change

Secondary Succession Occurs where an ecosystem previously existed Rebuilding of ecosystems destroyed by floods,

fire, earthquakes, farmland, … Mount St. Helens (1980)

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How Ecosystems Change

The first organisms to start rebuilding are known as pioneer species Usually mostly weeds, and plants that can survive

harsh environments These organisms make the land livable for other

species Eventually the ecosystem will stabilize into a

Climax Community A final and stable community This ecosystem will not change a lot over time

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How Ecosystems Change

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How Ecosystems Change

One of the biggest debates about succession is over forest fires

Fires are a natural part of an ecosystem Clean out brush, germinate seeds, enrich the soil

Of course fires also threaten homes, business, and communities

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United Streaming\The_Nitrogen_Cycle.asf

Phosphorus Cycle Ecological Succession

Primary Succession Secondary Succession

Pioneer Species Climax Community

Nitrogen Cycle Nitrogen-fixing Bacteria

Carbon Cycle Trophic Level

Food Web Food Chain

Cellular Respiration Decomposers

Consumer Producer

Photosynthesis Vertebrates

Invertebrates Angiosperms

Gymnosperms Protists

Fungus Bacteria

Habitat Community

Population Species

Organism Abiotic Factors

Biotic Factors Ecosystem