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Evidence of Species Change
Lesson 11.1 pages 378-383
7th Grade
Ms. Bertrand
Evolution
Evolution is a
change over time.
The scientific theory of
evolution explains how
living things descended
from earlier organisms.
Why does evolution occur?
 Evolution is a consequence of the interaction of four factors:
 (1) limits on the potential for a species to increase in number
 (2) the genetic variation among individuals in a species due
to mutation and sexual reproduction
 (3) competition for an environment’s limited supply of the
resources that individuals need in order to survive and
reproduce
 (4) the differential production of organisms with different
abilities to survive and reproduce in that environment.
THEORY=Supporting Evidence in Nature
There is evidence that supports the
theory of evolution
Fossils
Similarities in DNA and Protein
Structure
Similarities in Body Structure
Similarities in Early Development
Species
There are about 5 million different species
of organisms living on the Earth today.
However, fossil evidence suggests that
this is only a small percentage of the
number of all the species that have
existed on Earth.
Genetic Variation
A gene is a hereditary unit that can be passed on
for many generations.
The gene pool consists of the set of genes in a
species or population.
Different organisms differ in genes. Individuals of
the same species should not differ in the number
of genes.
Extinction
A species can go extinct for a variety of reasons:
They may have evolved into a new species
environmental changes
temperature changes
changes in rainfall can lead to extinction if the species
cannot adapt.
The disappearance of a species’ main food source.
Extinction will result if the species cannot find a
substitute food source.
Survival
 An organism’s survival depends on its inherited traits, which
influence its ability to compete for resources, procure mates, and
avoid danger to itself and its offspring. Both variation in the genetic
information among organisms in a population, and the expression of
that variation in genetic information that will lead to differences in
performance among individuals are necessary for natural selection
to occur. Traits that increase an organism’s chances of survival are
more likely to be passed on to future generations; thus, becoming
more common in the population.
Natural Selection
Natural selection is a process by which the
gene frequencies in a population change over
time because of the differential survival and
reproductive success of various genotypes
DSQ Answer
The Galápagos Islands are very dry, with an average
rainfall on some islands of only five inches per year.
The amount of rainfall has a large impact on the
availability and types of seeds that are available to
be eaten by finches.
In the process of natural selection, only the finches that are be
adapted to the available seed types survive and have offspring
Questions
Which beak allows the best chance of survival?
Which island allows the hairpin beak to survive the
best?
Which island allows the fork beak to survive the best?
Which island allows the clip beak to survive the best?
Which island allows the spoon beak to survive the best?
Which island allows the tweezer beak to survive the
best?
Darwin Lab
Data Analysis-MEAN Values
Island A
Beak 1
Beak 2
Beak 3
Beak 4
Beak 5
Beak 1
Beak 2
Beak 3
Beak 4
Beak 5
Beak 1
Beak 2
Beak 3
Beak 4
Beak 5
Beak 1
Beak 2
Beak 3
Beak 4
Beak 5
Beak 1
Beak 2
Beak 3
Beak 4
Beak 5
MEAN
Values
Island B
MEAN
Values
Island C
MEAN
Values
Island D
MEAN
Values
Island E
MEAN
Values