Transcript Evolution 2

EVOLUTION
EVOLUTION
Evolution is the gradual change of a species
over many generations.
Evolution is a theory. A scientific theory is a
well-tested concept that explains a wide
range of observations.
Hypothesis – an educated guess, a possible
explanation for a set of observations or
answer to scientific questions; must be
testable.
Law - A scientific law is a statement that
describes, predicts, and perhaps explains
why a wide range of phenomena behave as
they do in nature. (Newton’s laws of motion
or the law of gravity)
CHARLES DARWIN
Naturalist, Charles Darwin, was born
in England, on February 12, 1809.
In 1831, he embarked on a five-year
voyage around the world on the HMS
Beagle.
His studies of specimens around the
globe led him to formulate his theory
of evolution and his views on the
process of natural selection.
In 1859, he published The Origin of
the Species by Means of Natural
Selection.
He died on April 19, 1882, in London.
WHAT IS NATURAL SELECTION?
In Darwin’s book The Origin of Species, he
explained that evolution occurs by means of
natural selection.
Natural selection is the process by which
individuals that are better adapted to their
environment are more likely to survive and
reproduce than other members of the species.
• Species – a group of similar organisms that
can mate with each other and produce fertile
offspring. A mule is not a species because
they are not fertile and cannot mate with each
other. Mules can only be produced by
breeding a male donkey and a female horse.
• Adaptations – Traits that help an organism
survive and reproduce. (wings, claws, teeth,
camouflage, venom, speed and mimicry just to
name a few)
GALAPAGOS
One interesting place that Darwin visited was the Galapagos
Islands.
These islands are located about 600 miles from Ecuador,
South America.
Darwin noticed that the plants and animals on these islands
were similar to those in Ecuador, but not exactly the same.
Giant Tortoise
Blue-Footed Booby
Frigate Bird
Seal
Sally Light-Foot Crab
Iguana
DARWIN’S FINCHES
Darwin observed that the finches on the islands were different from
those in Ecuador. Their beaks were adapted according to how they
obtained their food. Beak shape is an adaptation that helps the
finches survive.
Darwin observed that other animals on
the islands were similar to the mainland
animals, but there were some important
difference.
For example the iguanas on the islands
had long, large claws for gripping rocks
and eating seaweed. The iguanas on the
mainland had smaller claws for climbing
trees and eating leaves.
He also observed large sea birds called
cormorants that lived in both places. The
mainland cormorants could fly, but the island
birds could not.
The tortoise on the islands had a dome shaped shell and the
mainland tortoise had a saddle shaped shell.
Darwin inferred that the plants and animal from the mainland,
were possibly blown to the islands by a storm.
Over time their offspring became different from their mainland
relatives.
The island species had to adapt to survive in their new
environment.
DARWIN’S THEORY OF NATURAL SELECTION
Darwin knew that people used selective breeding to produce
crops and animals with desired traits.
Darwin thought that a process similar to selective breeding must
happen in nature.
Darwin identified a number of factors that affected the process of
natural selection: Competition
Overpopulation
Darwin observed that many species produce more offspring than
can possibly survive. So many offspring are produced that there
is not enough resources – food, water, and living space – for all
of them.
Example
Each year a female sea turtle may lay more than 100 eggs. Some
of the eggs will survive and develop into adult turtles, and some
will not.
Struggle to Survive
Some sea turtle may be caught by predators,
and some may starve or get a disease. Only
some of the turtles will survive
Inherited Variation
Every individual organism has it own
combination of inherited traits. Each organism
is similar to, but not identical to, its parents.
Over along period of time , natural selection can
lead to evolution. Helpful variations gradually
accumulate in a species, while unfavorable ones
disappear.
Successful Reproduction
The sea turtles that are best adapted to their
environment are likely to have offspring that
survive.
EVIDENCE OF EVOLUTION
Evidence that organisms have
evolved is buried within the Earth's
crust.
Fossils – the remains or imprints of
once-living organisms that are
found in layers of rock and
sediment.
The dead organism is covered by a
layer of sediment , and over time
minerals in the sediment seep into
the organism and gradually replace
the organism with stone.
If the organism rots away
completely after being covered, it
may leave an imprint of itself in the
rock.
Evidence of Ancestry
Fossil Record – is a timeline
that gives the order in which
species have existed.
Fossil near the bottom are
the oldest and fossils near
the top are more recent.
Scientist observed that all
living things have
characteristics in common.
They think that all living
species descended from
common ancestors.
Branching Trees - are diagrams
that imply or infer that species
have descended from a
common ancestor. Scientists
use information about these
species to sketch out a “tree of
life” that includes all known
organisms.
HOMOLOGOUS STRUCTURES
Homologous structures provide evidence that these four organisms have all
evolved from a common ancestor. Notice that the bones in the forelimbs of
these four animals are arranged in a similar way.
EMBRYOLOGY
During the early stages of development all eight of the organisms have a
tail and tiny gill slits in their throats. These similarities suggest that these
vertebrate species are related and share a common ancestor.
DNA
Scientist infer that
species inherited
many of the same
genes from common
ancestors.
Techniques have been
developed that allow
scientist to extract
DNA from fossil
bones, teeth and from
insects trapped in
amber.
PESTICIDE AND PESTICIDE RESISTANCE
Pesticide and Pesticide resistance
ANTIBIOTIC AND ANTIBIOTIC RESISTANCE