Download common ancestor - Wando High School

 Charles Darwin (1809-1882) was an English
scientist who began as a naturalist aboard a ship
that sailed all over the world.
 Darwin became curious about the diverse
creatures that he saw and the possible
relationships between them.
 He searched for a reason why
organisms change over time
 He observed that there were many
struggles for survival: finding mates,
food, and shelter while escaping
predators and sickness
 From this he identified the process
of natural selection
 For years, people had bred specific organisms
to have certain traits – artificial selection
 Ex. breeding corn plants that produce the most ears
 Natural Selection occurs when organisms with
certain traits survive, reproduce, and pass on
those traits to the next generation.
 Ex: A faster fish may be better suited for escaping
predators and live to produce offspring with that same
variation
 A slower fish may be more easily caught by a predator
and never live to reproduce and pass on that trait
 This is often described as “Survival of the Fittest”
Overproduction of offspring – having many
offspring raises the chance that some will survive
2. Variation – Variation exists in the inherited
phenotypes of the individuals within every
population. An organism’s phenotype may influence
its ability to find, obtain, or utilize its resources
(food, water, shelter, and oxygen) and also might
affect the organism’s ability to reproduce.
Phenotypic variation is
controlled by the
organism’s genotype
and the environment.
1.
3.
Adaptation - The process of adaptation leads to the increase in
frequency of a particular structure, physiological process, or
behavior in a population of organisms that makes the organisms
better able to survive and reproduce.
 “Fitness” is used to measure how a particular trait contributes to the
reproductive success in a given environment and results from adaptation
4.
Descent with modification - As the environment
of a population changes, the entire process of
natural selection can yield populations with new
phenotypes adapted to new conditions. Natural
selection can produce populations that have
different structures, live in different niches or
habitats from their ancestors. Each successive living species will
have descended, with adaptations or other modifications, from
previous generations.
Most scientist attribute the continuity of life-forms over
time to the genetic processes that all organisms
share:
1. All life that has ever existed on Earth share at least
the same two structures:
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2.
Nucleic Acids (DNA or RNA) that carry the code for
the synthesis of the organism’s proteins
Proteins which are composed of the same twenty
amino acids in all life forms
The same sequences of nucleotides code for the
same specific amino acids.
Sexual
Asexual
 Genetic Varity Due to:
 Genetic Varity: can only
 Gene shuffling,
crossing-over,
recombination of DNA,
mutations
 Genetic changes result in
changes in the phenotype
 Different allele
combinations produce
traits that can improve
individuals chances of
survival
occur through mutations
in DNA passed from parent
to offspring
 Examples:
 Binary fission, budding,
fragmentation,
vegetative propagation
 Offspring are generally
genetically identical to
their parent
 All the genes, including different alleles, in a given
population is called the “gene pool”
 Diversity within a species makes it more likely that the
right adaptation could be present – therefore, an
increase in diversity increases its chances of survival
1.
Genetic Drift - the random change in the frequency
of alleles of a population over time. Due to chance,
rare alleles in a population will decrease in
frequency and become eliminated; other alleles will
increase in frequency and become fixed
2.
Gene Flow - the movement of genes
into or out of a population. This occurs
during the movement of individuals between
populations (such as migration) thus increasing the
genetic variability of the receiving population.
3. Non-random Mating – Mating among
individuals with favorable traits (such as
coloration or odors in plants and animals,
competitive strength, courting behaviors) results
in the gene pool of a population that can change
over time and a species that can become
increasingly adapted to its environment.
4. Mutations - increase the frequencies and
types of allele changes within the
population
5. Natural Selection - allows for the most
favorable phenotypes to survive and
thus be passed on to future generations.
 When there is no change in the allele frequencies
in a species, the population is in genetic
equilibrium.
 This concept is known as the Hardy-Weinberg
Principle. To sustain equilibrium, the must be:
 A very large population with no genetic drift
 No movement into or out of the population
 Random mating
 No mutations with the gene pool
 No natural selection
Godfrey Hardy
(1877-1947)
Wilhelm Weinberg
(1862-1937)
 The changes in inherited traits in a species over time is
called biological evolution.
 Microevolution occurs on a small scale affecting a single
population
 Macroevolution occurs on a large scale affecting changes in
species across populations
 We can look at common adaptations to trace the history of
different organisms and see how they may have evolved from a
common ancestor.
 The species we see today evolved from species of former periods
in time
 Other Evidence of Evolution
 Paleontology
 Anatomy
 Embryology
 Biochemistry
 Paleontology is the study of prehistoric life
 Fossils are preserved remains of organisms that lived
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many years ago
Comparing current and ancient species shows a pattern of
gradual change from the past to the present.
Examining the fossil record of Earth reveals the history of
organisms that have lived on Earth (including those that are
extinct) and the relative ages of those fossils.
The fossil record is not complete because most organisms
do not form fossils. Many of the gaps in the fossil record
have been filled in as more fossils have been discovered.
The older the fossils, the less resemblance there is to
modern species.
 Anatomy is the study of the structures of organisms
 Structures in different species
with common evolutionary
origin are called
homologous structures
 The can be similar in:
 Arrangement
 Function
 Both
 Scientists view homologous structures as evidence of a
common ancestor because it would be unlikely for so
many animals to have similar structures if they developed
individually.
 The study of evolutionary relationships between
homologous structures is called Comparative Anatomy
 Similar function of a body
feature does not always mean
they have a common ancestor.
 The wings of birds and insects
evolved from distinctly
different groups of ancestors.
 Though their wings are alike in
function, they differ in
structure.
 Body parts of organisms that
do not have similar ancestry
are called analogous
structures.
 Vestigial Structures also provide evidence of
common ancestry.
 Vestigial Structures have little or no function in an
organism but were probably useful to an ancestor.
 Example:
 Our tailbone (coccyx) – has no current
function but may once have
been helpful to our ancestors
 The eyes of blind mole rats
 Pelvis of a snake
 The muscles in human ears
 Embryology is the study of embryo development in
organisms
 The could include pre-birth, pre-hatching, or pre-germination
 The study of this development in different species is called
comparative embryology
 Studying the structures of embryos can lead to clues of
possible ancestors
 The embryos of fish, reptiles, birds, and mammals all have
a tail and gill slits even though they may not exist on the
mature organism
 Biochemistry is the study of chemical processes
in organisms
 The study of the ability of different species to
synthesize substances is called comparative
biochemistry.
 Comparison of the DNA sequences of two species
provides some of the most reliable evidence.
 Organisms with the common ability to synthesize
a specific substance may be evidence of a common
ancestor.
 All citrus trees can produce citric acid
and therefore may have developed
from a common ancestor
 Speciation is the process of forming a new species by
biological evolution from a preexisting species
1. Gradualism - Gradual changes of a species in over long
periods of time
 Ex - gradual trend toward larger or smaller body size.
2. Punctuated Equilibrium - Periods of abrupt
changes in a species after long periods of little
change within the species over time
 Ex - sudden change in species size or shape due to
environmental factors
3. Divergent Evolution - a number of
different species diverge (split-off) from
a common ancestor. This occurs when,
over many generations, organisms (whose
ancestors were all of the same species)
evolve a variety of characteristics which
allow them to survive in different niches.
4. Convergent Evolution - Evolution among different
groups of organisms living in similar
environments produce species that are similar in
appearance and behavior. Convergent evolution
has produced many of the analogous structures in
organisms today.
5.
Coevolution - when two or more species living in
close proximity change in response to each other.
The evolution of one species may affect the evolution
of the other.
6. Extinction - the elimination of a species often
occurring when a species cannot adapt to a change in its
environment. This can be gradual or rapid.
 Gradual extinction - occurs at a slow rate and may be due to other
organisms, changes in climate, or natural disasters.
 Mass extinction - occurs when a catastrophic event changes the
environment very suddenly (such as a massive volcanic eruption,
or a meteor hitting the earth causing massive climatic changes). It is
often impossible for a species to adapt to rapid and extreme
environmental changes.
the relationship of different
organisms believed to have a
common ancestor based on
taxa (groups)
 Branches from an
intersection show those with
a common ancestor
 You can see that the snail,
earthworm and insect have a
more recent common
ancestor than the snail and
sea star
Time
 A Phylogenetic Tree shows
 All living things can be classified as belonging to
one of 3 Domains
 Bacteria
- Archaea
- Eukarya
 All living things can be classified as belonging to
one of the 6 Kingdoms of Life
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Archaeabacteria
Eubacteria
Protista
Plantae
Fungi
Animalia
A dichotomous key is a tool that allows the user to determine the
identity of items in the natural world, such as trees, animals, or rocks.
Keys consist of a series of choices that lead the user to the correct name of
a given item. "Dichotomous" means "divided into two parts". Therefore,
dichotomous keys always give two choices in each step.
1. a. wings covered by an exoskeleton ………go to step 2
b. wings not covered by an exoskeleton ……….go to step 3
2. a. body has a round shape ……….ladybug
b. body has an elongated shape ……….grasshopper
3. a. wings point out from the side of the body
……….dragonfly
b. wings point to the posterior of the body ……….housefly