Download Ecosystems and Evolution

Ecosystems and Evolution
What is an ecosystem?
An ecosystem are made up of:
• Organism: one individual
living thing.
– An example: a single ant
walking up a tree
• Species: is a group of
organisms that are able to
reproduce together and
share common genes and
therefore resemble each
other.
– All humans, for example, are
members of the species
Homo sapiens.
What is an ecosystem?
An ecosystem is made up
of:
• Population: groups of
the same organisms
living in the same area
– An example of a
population is a pride of
lions in the Savanna
What is an ecosystem?
An ecosystem includes:
• Communities: various populations living together and
interacting with each other
• An example of a community is plants, fish, insects, amphibians
and microorganisms that live in and around a pond.
What is an ecosystem?
• An ecosystem includes
all the different
organisms living in a
certain area and their
physical environment
• An ecosystem is
composed of both
biotic and abiotic
factors
What is an ecosystem?
• Biotic factors of an
ecosystem include:
animals, plants and
microorganisms
• Abiotic factors of an
ecosystem include:
temperature, sunlight,
humidity, water supply,
soil type, and mineral
nutrients
Within an Ecosystem…
• Consider a lion living in the savanna. Lions survive by
eating other animals (gazelles, zebras and wildebeests).
After the lions have eaten their fill, scavengers like
vultures and hyenas will eat the rest. Bacteria, fungi
and insects also feed on the carcass. The lion is also
food for other animals: ticks, fleas, mosquitos all drink
the lion’s blood. The lions dung feeds organisms like
worms and insects that live in the soil…
• All of the lion’s relationships with its environment, both
the living and non-living parts make up its niche…
Within an ecosystem
• A niche is an organisms
way of life. The niche
includes relationships,
how often it reproduces,
how many offspring it
has, what time of day it is
most active, where it
finds shelter, what it
eats…
– Basically a niche is the role
of an organism within an
ecosystem
Within an ecosystem
• The actual place an
organism lives is called
its habitat.
– The lion’s habitat is the
savanna
– A howler monkey’s
habitat is the rainforest
– A cactus’s habitat is a
desert
– A water lily’s habitat is a
pond.
Interactions
• Species within an
ecosystem can affect
each other… both
positively and
negatively.
• There are five major
types of species
interactions
Interactions
• Predation: one
organism kills and eats
another organism
• The organism that is
eaten is called the prey
and the one that does
the eating is called the
predator
• An example: a snake
(predator) eats a mouse
(prey)
Interactions
Competition: a relationship
between species in which they
attempt to use the same
limited resource. There is a
struggle between the two
species to use the resources.
• Example: a hyena and
vultures fight with each
other over who gets to eat a
dead animal
• Example: two trees race to
grow taller than the other
as they compete for
sunlight
Interactions
Parasitism: when an
organism lives in or on
another organisms and
feeds on it without
immediately killing it.
• Parasite: the organisms
feeding on the host
• Host: the organism that is
being used by the
parasite
• EXAMPLE: fleas on a dog,
pinworms in a human and
ivy on a tree
Interactions
Mutualism: a cooperative
partnership between two
species. It is a relationship
that is good for both
organisms
Example:
– Healthy bacteria living in our
intestines. Healthy bacteria
help to digest food, break
down nutrients, and
produces necessary
substances your body
cannot make like vitamin K…
humans provide the
bacteria with a safe. food
rich and warm place to live.
Interactions…
Commensalism: A relationship
in which one species benefits
and the other is neither
harmed nor helped.
Example: Sharks and crabs.
Sharks eat fish at the surface
of the ocean. The food scraps
float down to the bottom of
the ocean floor and crabs can
eat the pieces of fish. The
shark has no interest in the
crabs… but the crabs NEED the
shark to help provide them
with food.
Evolution
• Organisms tend to be well suited to their
environments… kangaroo rats, for instance, are
well suited to the deserts where there is little
water. The kangaroo rats cope with this dry
environment by conserving water in their bodies.
They eliminate very little water in their urine and
feces. They do not sweat. They are active at night
when it is cooler. Kangaroo rats are so effective at
saving water, that they never need to drink it,
they get all their water from the food they eat!!
Evolution
Evolution by Natural Selection• Darwin used the term
natural selection to describe
the unequal survival and
reproduction that results
from the presence or
absence of particular traits
• Darwin proposed that over
many generations natural
selection causes the
characteristics of
populations to change
Evolution
• A change in the genetic
characteristics of
populations from one
generation to another is
known as evolution
• Understanding natural
selection is important in
understanding ecology…
all the relationships in
ecology come from how
organisms have evolved
together over time
• There are five rules of
natural selection
Rules of Natural Selection
All organisms have the ability
to produce more offspring
that can possibly survive
• Example: a female cod fish
pays millions of eggs. If all
these eggs hatched and the
young grew to adulthood
the world would be flooded
with cod… of course most of
them don’t survive. They
are eaten, aren’t good
swimmers, don’t blend in
with their environment,
have genetic defects…
Rules of Natural Selection
There is a struggle for existence.
• The environment contains things that kill organisms. The
environment is often hostile: hot or cold, dry or flooded…
predators are common and the resources needed to survive and
reproduce: food, water, living space, light- are often in short
supply. Therefore, individuals compete for these limited resources.
Rules of Natural Selection
Individuals vary, or differ, in
their traits
• Organisms of the same
species may differ in size,
shape, coloration, running
speed, resistance to disease
and many other traits. This
variation must be inherited
for it to influence natural
selection
• Organisms with traits better
suited to their environment
survive better than those
who don’t.
Rules of Natural Selection
Evolution by Natural Selection:
• Because individuals with advantageous traits have
more offspring, each new generation contains a greater
number of offspring with these traits than did the
previous generation. Since these traits are inherited,
offspring with the advantageous traits become more
numerous in the next generation. Individuals without
the trait become less numerous. Gradually, over many
generations, the population contains more and more
individuals with the advantageous trait… the
population is evolving to be better and better suited to
its environment.
Adaptations
• Adaptations are
inherited traits that
increase an organism’s
chance of survival and
reproduction in a
certain environment
• EXAMPLE: a moth with
speckled wings can hide
better on the bark of
trees than a moth with
solid wings.
Adaptations
• Mimicry: a structural
adaptation that enables
one species to resemble
another species.
• Usually mimicry is a
harmless species
resembling a harmful
species
• Example: a non-poisonous frog
looks like a poisonous frog or a
fly has yellow and black stripes
to look like a bee… predators
avoid the mimicking organism
Adaptations
• Camouflage- an
adaptation that enables
a species to blend with
their environment. This
helps them to avoid
getting eaten or to stalk
prey
• Example: a stick bug
looks like a plant or a
jaguar blends in with
the forest
Adaptations
• Structural adaptationphysical features of an
organism like the bill on
a bird or the fur on a
bear that help the
organism survive better
in its environment.
Adaptations
• Behavioral Adaptationsare the things that an
organism does to
survive
• Examples:
– Birds migrate the south
for the winter
– Whales sing to each
other
– Elephants remember
previous trails to water
Adaptations
• Physiological Adaptations- are
adaptations of metabolic or
internal processes.
– Animals pheromones or scent
to identify others
– Bacteria becoming resistant
to antibiotics
– Humans becoming immune
to viruses they have already
had
– Frogs being able to change
gender if there is no one to
mate with of the opposite
gender
– Camels bodies store fat and
water in humps
Types of Selection
• Sometimes species are stable and constant.
Their species is not evolving
• Other times species are all evolving in the
same direction together
• New species can form when one species has
two very different advantages for survival and
they evolve in different directions
Types of Selection
• Stabilizing selection- Natural selection that
favors the average individual
– Consider a population of spiders where average
size is the survival advantage. Too bog and birds
can see them, too small and they cannot find
enough food. In this environment the average
sized spider is more likely to survive and pass on
its genes
Types of Selection
• Directional Selection- natural selection that
favors one of the extreme variations of a trait
– A population of woodpeckers feeds on insects
living deep in the bark. Only woodpeckers with
the longest beaks could feed on that insect. Long
beaked birds would survive better than average or
small beaked birds
Types of Selection
• Disruptive Selection- natural selection that
favors individuals with either extreme of a
trait’s variation are selected for
– A population of clams with shells of white, tan and
dark brown line on a beach. All of the rocks on the
beach are either very light or very dark. All of the
light clams survive on the light rocks, and all of the
dark clams survive on the dark rocks. So it is a
strong disadvantage to be tan.
The evolution of the species
• Speciation--The evolution of new species. It
occurs when members of similar population
no longer produce fertile offspring within their
natural environment
• Species- group of organisms who look similar
and can interbreed.
•
Coevolution
• An organism’s
environment includes not
only physical aspects such
as climate, but also other
organisms, which can be
strong forces in natural
selection
• When two or more
species evolve in
response to each other it
is called coevolution
Coevolution
Examples of coevolution:
• Predators and prey… as
prey become better at
camouflage and
running, predators must
be better at seeing
them and be faster.