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1. Exploring Evolution

2. Learning Outcome
- Describe the evidence of
evolution such as homology,
DNA/protein sequences, plate
tectonics, the fossil record,
embryology, and artificial
selection/agriculture.

3. Whatis evolution?
- Evolution: The gradual change in
species over many generations
resulting from their genetic
adaptation to the environment.

4. Evidence of Evolution
1. Fossils:
- A fossil is the remain or evidence of a living thing.
- Most fossils are formed when an organism becomes buried in
sedimentary rocks.
- Scientists use radioactive dating techniques to determine the
age of rocks an

5. - The growth and development of an embryo are controlled by
genes.
- Similarities in the early stages of embryo development show that
organisms evolved from the same ancestor.
Embryological evidence:

6. Homologous structures:
- The age of fossils is used to determine the characteristics of the
layers of sedimentary rocks where the fossils are found.
- Similarities in the shape and arrangement of bones show they
evolved from the same ancest

7. 4. DNA AND PROTEIN
SEQUENCE:
- Similarities in DNA and protein
sequences show that two or more
organisms are closely related.

8. VESTIGIAL STRUCTURES
- A vestigial structure is a body part that is
reduced in size and does not seem to have a
function.
- Example: The tiny leg bones of snakes
suggest that they evolved from an ancestor
that had legs.

9. THEORIES OF EVOLUTION
1. Theory of Acquired Traits (Jean Baptiste de Lamarck)
- Organisms desire to improve themselves and become more advanced.
- Effort to improve causes some body structures to be constantly used,
while unused structures weaken and disappear (principle of use and
disuse).
- Modifications of structures due to use or disuse are inherited by offspring
(inheritance of acquired characteristics).
- Example: A giraffe's neck becomes longer to reach food, and this longer
neck is passed on to its offspring.

10. 2. Theory of Natural Selection (Charles Robert Darwin)
- The number of offspring is usually greater than the available
resources necessary for survival.
- Every organism must struggle to survive.
- Some variations allow members to survive and reproduce better
than others.
- Organisms that survive and reproduce pass their traits to their
offspring, and helpful traits gradually appear in more offspring.

11. Factors That Bring About
Organismal Diversity
1. Mutation:
- Changes in the chromosomes of organisms that are heritable and permanent.
- Mutations can be changes in quantity or quality.
- Mutations are responsible for the evolution of a group of organisms from one
generation to another.
- Examples: Albinism, sickle cell anemia, and cystic fibrosis.

12. 2. Genetic Drift:
- Evolution by chance.
- Refers to an increase or decrease in the
relative abundance of different cells through
successive generations.
- It is a random fluctuation in allele frequencies
over time.

13. 3. Gene Flow:
- A change in allele frequencies due to
immigration (new individuals enter the
population) or emigration (some
individuals leave).
- Gene flow among organisms is based on
the physical dispersal of alleles and tends
to decrease divergence that might arise
through other evolutionary factors.

14. 1. Natural Selection:
- In any population, more offspring tend to be produced
than can survive to reproductive age.
- Members of the population vary in form and behavior.
- Some heritable traits are more adaptive than others,
improving chances of survival and reproduction in
prevailing environmental conditions.
Key Concepts in Evolution
and Classification

15. 2. Speciation:
- A new species is formed when individuals of a
population continue to breed among themselves over a
long period and accumulate a new set of traits unique to
them.
- These traits are already different from those of the
original species.

16. 3. Adaptation:
- Adaptation refers to the process whereby a species can
tolerate the environmental conditions of a place and
efficiently compete with other species.
- If environmental conditions change drastically, only
species with adaptations to new conditions will survive.

17. 4. Classifying Organisms Based on Evolutionary
Relationships:
- Modern classification started with the work of Carolus
Linnaeus, classifying organisms by their similarities.
- The Linnaean system divides living things into
kingdoms (like plant and animal).
- Within each kingdom, organisms are divided into phyla,
then classes, orders, families, genus, and species.

18. Significance of Classifying Organisms
- Systematic Organization: Classification
provides an easy and systematic way of
finding a category where an organism belongs
and how it relates to others. As you go down
the scale from kingdom to species, the
resemblance between organisms becomes
much closer.

19. - Relationship and Origin: Classifying
organisms shows the relationship of
organisms, traces the possible origin of
organisms, and the development of their
present forms.

20. - Evolutionary Mechanisms:
Taxonomy goes beyond naming and
classifying organisms to clarify new
methods and theories to explain the
mechanisms of evolution.

21. - Common Descent: The principle
behind the evolutionary states that
similarities among organisms are due
to common descent, or inheritance
from a common ancestor.

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