occurence of evolution

1. WELCOME TO OUR
SCIENCE CLASS!

2. Picture Analysis

3. Picture Analysis

4. Picture Analysis

5. Theories of Evolution

6. • Explain the different theories
concerning evolution;
Lesson Objectives
• Compare Darwinian and other
theorist’s view of evolution; and
• Show appreciation on biological
evolution..

7. Jean Baptiste de Lamarck
Jean Baptiste de
Lamarck was the first
evolutionist to believe
that organisms change
over time.

8. Lamarck’s Theories

9. Lamarck’s
Theories
Theory
of Need
Theory of
Use and
Disuse
Theory of
acquired
characteristics

10. Theory of Need
The theory of need states that organisms
change in response to their environment.
Their ability to survive helped them
develop characteristics necessary for them
to adapt to a given environment.

11. Theory of Need
According to Lamarck, the ancestors of giraffes
had short necks before, but because of drought
and scarcity of food, they were forced to change
the structure of their necks by forcing them to
reach the higher sources of food for them to
survive. Their ability to survive helped them
develop characteristics necessary for them to
adapt to a given environment.

12. Theory of Use
and Disuse
According to him, organs not
in use will disappear, while
organs in use will develop.

13. Theory of Use and Disuse
According to him, organs not in use will disappear,
while organs in use will develop. Again, it is like in the
first theory where Lamarck believes that giraffes had
short necks before, but because of the need to survive
and in order to reach tall trees for food, they kept
stretching their necks until they became longer and able
to reach taller trees.

14. Theory of acquired
characteristics
Lamarck believes that these acquired
characteristics were believed to be
inherited by their offspring and
propagated by the next generation.

15. But many scientists rejected the theories of Lamarck.
They understood that if there were changes in the cell
or body structure, there could be changes in the
genetic information of the species.
For example, if you change the color of your hair by
dyeing it from black to blonde, do you think class,
your child will inherit the blonde color of your hair?

16. Darwin’s Theory
In natural selection, environment factors
promote the survival of the fittest and
eliminate the less fit. Organisms which
can adapt to their environment have a
better chance of survival and have the
capability to reproduce their own kind.

17. According to Darwin, originally, giraffes had
varying neck lengths. Natural selection
favored the survival of long-necked giraffes
because it allowed them to reach for food in
tall trees while short-necked Giraffes were
eliminated because of their inability to
reach higher vegetation when there was a
scarcity of low vegetation such as grass.
This eliminated them from the population of
giraffes.

18. Charles Darwin traveled to
different islands until he found
Galapagos Island, where he
found different finch bird
species.

19. He observed that finches have
different beak structures for
different food types. The
abundance of finch species on an
island was somehow related to
the type of available food for
these birds. Darwin suggested
that selection takes place in
nature.

20. Did you know class organism struggle for existence in
order to survive because they need to compete for food
and space and also adapt the changes in environment.
In real life, animals migrate and find other mates, gene
continually mutate, and nature allows the fittest
organism to survive. When these conditions happen,
evolution has occurred.

21. Mechanism of Evolution
Individuals’ choice of mate is
influenced by some physical
and behavioral characteristics.
NON-RANDOM MATING MUTATION
The organism’s appearance is dictated
by the information stored in its
chromosomes. So, if the chromosome’s
structure or gene composition is
changed, the appearance of the
organism will also be changed.

22. Mechanism of Evolution
Genetic drift means a change in gene
pool due to chance alone.
Unpredictable disasters and diseases
can reduce or totally eliminate certain
traits in a population.
GENETIC DRIFTING GENE FLOW
Gene flow or genetic
exchanges similar to these
make a population more
diverse.

23. Mechanism of Evolution
Natural selection by which nature
selects which traits will survive
and which will not. These
organisms with favorable traits,
are those who are best suited to
the environment and have a
better chance of survival.
NATURAL SELECTION

24. SPECIATION
Speciation is a process within
evolution that results in the
formation of new, and distinct
species that are
reproductively isolated from
other population when there is
no gene flow.

25. Types of Speciation
It occurs due to geographical
isolation and both species evolve
separately. The original population
is divided into two by a barrier
resulting in reproductive isolation.
ALLOPATRIC PERIPATRIC
The process of speciation occurs at a small
level, where geographical barriers separate the
species at the periphery isolating the small
population. Evolution occurs separately. Occurs
when the size of the isolated subpopulation is
small.

26. Types of Speciation
Species in this process of speciation
spread out over a large geographic area
but individuals only mate with those in
their own geographic region.
PARAPATRIC SYMPATRIC
The formation of new species
from an original population that
are not geographically isolated.

27. Let's review
1. What are the three
theories of Jean Baptiste
de Lamarck?
2. How natural selection
of Charles Darwin
happens?
3. What are the
mechanisms of
evolution?

28. To test whether you've learned something today, I
prepared 10-item multiple choice type of test to be
answered individually.
Evaluation

29. Directions: Choose the letter of the best answer. Write the chosen letter before
the number
1. Which of the following causes of evolution states that sexual selection is not merely by
chance?
A. Non-random mating
B. Genetic Drift
C. Gene Flow
D. Mutation
2. What is genetic drift?
A. The formation of new species.
B. A change in gene pool due to chance alone.
C. Any change in the structure of chromosomes and gene composition.
D. The migration of individuals from one population to another.

30. • 3.During the process of speciation, a species is first isolated _______.
• A. genetically
• B. behaviorally
• C. geographically
• D. reproductively
• 4.The following are statements thatdescribe Darwin’s theory of natural selection except___________.
• A. Members of a population will compete.
• B. Populations tend to reproduce in small numbers.
• C. Members of a population have heritable variations.
• D. Some members of a population have adaptive traits.
•
• 5. Which of the following mechanisms will cause the gene pool of two populations to change?
• A. Mutation
• B. Gene Flow
• C. Genetic Drift
• D. Natural Selection

31. 6. Which of the following describes mutation?
A. A result of inbreeding.
B. Any change in the structure of chromosomes.
C. Change in gene pool due to migration.
D. Differential survival and reproduction of organisms.
• 7. What agent of evolutionary change can result to a population with limited variation due entirely to
chance?
• A. Mutation
• B. Gene flow
• C. Genetic drift
• D. Inbreeding
•
• 8. What do you call the process that results to the formation of new species because of evolution?
• A. Speciation
• B. Mutation
• C. Reproduction
• D. Migration

32. 9. Who is the first evolutionist to believe that organisms change?
A. Jean Baptiste de Lamarck
B. Richard Dawkins
C. Charles Darwin
D. Steve Jones
10. It is commonly observed in plants and in some kinds of animals and a very good example of non-
random mating.
A. Genetic drift
B. Inbreeding
C. Gene flow
D. Mutation

33. Agreement
A. Follow-up:
Directions: Answer the following question concisely.
1. Cite some examples on the different mechanisms of evolution?
2. Imagine that you are one of the scientists during the past, which theory would
you accept? The theory of Darwin or Lamarck? Why? Briefly explain your
answer.
B. Advanced:
Directions: Give a brief response to the following question.
1. What is adaptation?
2. What are the different ways organisms in adapting the environment?
3. Why it is necessary to adapt the changing environment?

34. THANK YOU!