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Transcript
 Biological
Evolution:
“Change in the genetic composition of a
population during successive generations
(due partly to natural selection) and
resulting in the development of new
species” (Webster’s).
The ancestors of the
horse, for example,
have undergone
considerable change in
physical size and
proportions over the
last 60 million years.
 The
adult size, shape,
bones, internal organs
and many other
physical and
behavioral features
have changed.
 The original Eohippus
was thus a different
“type of animal”
(species) than the
present day horse
(Equus)
Such changes in body parts
are the result of changes in
genes.
When nature “selects” the
“fittest” for survival and
reproduction, it is also
selecting the fittest
combination of genes to
survive and reproduce.
These come “packaged” in
a creature’s body.
 Biological
Evolution
happens through
transmission of genetic
characteristics from one
generation to the next
 Individuals who are the
most genetically “fit”,
survive to reproduce
(called natural selection
or “survival of the fittest”)
and pass on their fit
characteristics
 “Natural
selection” is a metaphor which
Darwin compared to “artificial selection”
(the breeding of plants & animals).
 Artificial selection = humans “select”
which individual plant or animal will
reproduce.
 Natural selection = nature does this
“selecting”.
Varieties of
bananas
produced by
artificial
selection
Note how all these
dramatically different
vegetables were created
by artificial selection from
an original ancestor.
How does Natural Selection work?
 Four
main Principles of Natural Selection
• 1. Variation
 tendency for individuals in a species to differ slightly from their parents
and from each other (genetic recombination/mutations).
• 2. Overproduction
 While having many offspring raises the chance that some will survive,
not all will survive due to competition for resources.
• 3. Adaptation
 Certain variation allows an individual to survive better than other
individuals it competes against. More successful individuals are
“naturally selected” to live longer and produce more offspring that
share those adaptations for their environment.
• 4. Descent with Modification
 Over time, natural selection will result in species with adaptations that
help it survive and reproduce. More individuals will have the trait in
subsequent generations, as long as the environmental conditions remain
the same.
Important Note:
Adaptations do not give an individual
or species what they “need” to
survive.
The “best” or most “fit” features are
“naturally selected”

An adaptation is a structure, behavior or
physiological process

Help an organism to survive and reproduce
in particular environment

Adaptations are inherited from their parents

It also refers to the ability of living things to
adjust to different conditions within their
environments.
 Structural
adaptation involves some
part of an organism's body.
Teeth
Body coverings
Shells
Quills
Scales
Camouflage
Mimicry


Camouflage allows an
animal to blend into its
environment.
Makes it hard for
enemies to single out
individuals

Mimicry allows one
animal to look, sound, or
act like another animal
to fool predators into
thinking it is poisonous
or dangerous.




Vascular-stems
Root systems
Thorns
Leave type
 Broad:absorb more
sunlight
 Small needle-like:
reduce water loss
 Waxy: reduce water
loss, protect from fire
 Poisonous/toxins

Behavior adaptations
include activities or
behaviors that help an animal
survive.
1. Innate
2. Learned
3. Survival
4. Seasonal
INNATE


Inherited through the
genes
Examples
 Flying for bees, birds
 Swimming for fish
 Walking for humans
 Speaking for humans
LEARNED


Learned from experience
or from observing other
animals
Examples
 Type of language spoken
for humans
 Riding a bicycle
1.
2.
3.
4.
5.
Finding food
 Predator-Prey adaptations
Predator-animals that eat other animals
Prey-animal being eaten
Marking Territory
 Way that animals inform other animals that an area is
occupied
Defensive Action

Protect resources, themselves, food, mates, offspring
Courtship
 Behaviors used to find a mate
Parenting

Depend on parents for survival

Some animals use these
methods of defense to
protect themselves:
 Camouflage
Snake
 Mimicry
Mexican Milk Snake
 Bright colors
Skunk and Poison
Arrow Frog
 “Hair” projections
Hedgehog quills
Deer Antlers
 Help
1.
2.
3.
4.
organisms adapt to the environment
Migration
Hibernation
Estivation
Biological Clock
 Behaviors
controlled by the brain
Reflexes
Blinking
Pain
Swallowing
Tolerance to a certain poison
Logical thinking


Warm-blooded
All have some type of
“hair”
 Some are very
specialized, such as
white polar bear fur

Care for young

Leg Length
 Roseate Spoonbill
(top right)

Foot Webbing
 Laughing Gull
(top left)

Beak Shape
 Long Billed Curlew
(bottom)





cold- blooded
Scales
Some undergo
hibernation and
estivation
Lay eggs on land
Leg structure and
position




Cold-blooded
Lay eggs in water
Partially of fully
webbed feet
Have lungs or can
absorb oxygen through
their skin
Depends on reproductive success
Operates on a population, NOT on an
individual
Dynamic between genetic change and the
changing environment
Environment exerts selective pressure:
environmental conditions that select for
certain individuals and select against others
Natural Selection can take time or can
happen quickly



Fossils
• Allow us to visually see organisms change over time
Geography
• Being able to see the distribution of organisms around
the world
Embryology
• Similar features of embryos in very different
organisms suggest evolution from a distant common
ancestor


Anatomy
• Homologous structures – features that are similar in
structure but appear in different species offers strong
evidence for common descent.
Vestigial structures
• Underdeveloped or unused features are remnants of organs
or structures that had a function in an early ancestor.
Snakes have tiny pelvic bones that are homologous to lizards
but are not needed. Ostrich has wings that have little or no
use now.