About evolution

1. JIMMA UNIVERSITY COLLEGE OF NATURAL
SCIENCE
EVOLUTION GROUP ASSIGNMENT
DEPARTMENT OF BIOLOGY

2. Members ID Number
Tamirat Kassa Ru 2091/12
Hamza Adem Ru 0875/12
Abayneh Adore Ru 1961/12
Cherinet Eyasu Ru 2029/12
Kassahun Jemal Ru 0075/12
Bethelhem Aschalew Ru 1845/12
Selam Zemenu Ru 0695/12
Group 2

3. Pre Darwin thought
In Darwin’s time scientists were beginning to realize that the world
was much older than previously thought
A.before Darwin the accepted age of the earth was determined by
James Ussher (1581-1656) & John Lightfoot (1602-1675)
 made assumption that the Bible was the only reliable source of
chronological information for the time covered in biblical writings
 arrived at the calculation that the earth was created onSunday,
October 24, 4004 BC
 Lightfoot, making additional assumptions put the time at 9:00 am
 so the earth was believed to be ~6000 years old

4. Pre Darwin thought...
b. in the next century, Comte de Buffon (1707-1788;
 “Histoire Naturelle”, 1749) believed he could get an estimate of the
age of the earth based on its rate of heat loss
 he calculated the age of the earth as 74,832 yrs (and the origin of life
at 40,000 yrs)
 he also recognized 6 geological periods
 much of western science at this time was still dominated by Church
beliefs and he was heavily pressured by the Church to reconsider his
calculations
 his solution: “this is what one might think if one didnot know what
genesis says”

5. Pre Darwin thought.....
C. by Darwin’s time geologists were beginning to realize that the earth was
100’s of millions or even billions of years old
eg. paleontologists were learning that fossils were representatives of previous
forms of life from the ancient past
• much earlier, fossils were thought of as “sports of nature” by 1700’s most
scientists believe that fossils were of organic origin but most were explained in
terms of the Biblical flood
• as geologists were realizing the extreme age of the earth that that would mean
that fossils trapped in these ancient layers were also millions of years old
eg. previous biologists had already suggested that
all species are interrelated
species change through time
and the environment is a factor in that change
Jean Baptiste de Lamark (1809) produced the first “evolutionary tree” to illustrate
“change through time” but he could not offer a reliable explanation or
“mechanism for how these processes could occur

6.  The theory of evolution was developed by Charles Darwin, in the mid 1800’s, after a lifetime
of travel, observation, experimentation and discussion.
 Charles Darwin was a British naturalist who proposed the theory of biological evolution by
natural selection.12 February 1809 – 19 April 1882)
 Darwin defined evolution as "descent with modification," the idea that species change over
time, give rise to new species, and share a common ancestor.
 Darwin is considered the father of evolution. In truth, Darwin arrived at his theory of
evolution at the same time another scientist, Alfred Russell Wallace, came to the same
conclusion.
 However, Darwin was a respected scientist even before he wrote On the Origin of Species.
Theory of Evolution
Alfred Russell Wallace
Charles Darwin

7. Theory of Evolution
 The mechanism that Darwin proposed for evolution is natural selection.
 Darwin's theory consisted of two main points;
1. diverse groups of animals evolve from one or a few common ancestors;
2. the mechanism by which this evolution takes place is natural selection.
 Darwin's theory of evolution, also called Darwinism
It can be further divided into 5 parts:
1. Evolution as such,
2. Common descent,
3. Gradualism,
4. Multiplication of species, and
5. Natural selection.

8. 1.Evolution as such.
 This is the theory that the world is not constant nor recently created nor perpetually cycling
but rather is steadily changing and that organisms are transformed in time.
Evolution as such

9. Common descent
2.Common descent,
 This is the theory that every group of organisms descended from a common ancestor ,and that all
groups of organisms, including animals, plants, and microorganisms, ultimately go back to a 'Single
origin o f life on earth'.

10. 3.Multiplication of species
This theory explains the origin of the enormous organic diversity. It postulates that species multiply,
either by splitting into daughter species or ry ''budding,'' that is by the establishment of , geographically
isolated founder populations that evolve into new species
Multiplication of species

11. • Evolution is a process of gradual development in a particular situation or thing over some
time.
• In Biology Evolution is the change in heritable traits of biological populations over
successive generations. Evolutionary processes give rise to diversity at every biological
organization level. All life on earth shares a common ancestor known as the last universal
ancestor.
• Evolution is one of the most fundamental organizing principles of the biological sciences and
as such is the single most dominant theme in biology today
Evolution

12. Gradualism
4 .Gradualism
 According to this theory, evolutionary change takes place through the gradual change of
populations and not by the sudden (saltaional)production of new individual's that represent a
new type.

13. Natural selection
5.Natural selection
 According to this theory; evolutionary change, comes about through the abundant production of genetic
variation in every generation. The relatively few individuals who survive, owing to a particularly well-
adapted combination of inheritable characters, give rise to the next generation.

14. Natural selection
 Natural selection is a simple mechanism that causes populations of
living things to change over time.
 In fact, it is so simple that it can be broken down into five basic steps,
abbreviated here as VISTA:
 Variation,
 Inheritance,
 Selection,
 Time and
 Adaptation

15. Theory of Evolution
The Theory of Evolution by Natural Selection at its core is a relatively simple idea:
A.Variation
 all living things consist of a unique combination of chemicals organized in unique
ways.
 In all species, individuals differ in their genetic makeup, producing many variations in
their physical features; individuals in a population vary from each other.
 variations occur in every species which means no two individuals of a species are
alike
B.Inheritance
 most of these variations have a genetic basis
 they can be passed on to their offspring
 Darwin was not aware of Mendel’s work,
 He didn’t know HOW traits were passed on, just observed that some were took
another 50-60 yrs before hereditary information was added to Darwin’s original
theory
 made it even more powerful
Natural selection

16. 1
C.Selection
those individuals whose variations best fit their environment will be
more likely to survive and reproduce
fittness = ability to reproduce
 organisms with less favorable variations will be less likely to survive
"There is a “struggle for existence”
" with “survival of the fittest”
D.TIME
 each species produces more offspring than will survive into maturity
eg. if not, 1 bacterial cell -> 36 hours would cover earth 3-4 ft deep
eg. fruit fly -> in 7 months would produce enough offspring to equal
the mass of the earth
Natural selection

17. Natural selection
E.Adaptation
species’ populations are able to adapt to gradually
changing enviromnts.
same species in different parts of the world have
different tolerances and slightly didiffere tharacteristics to
survive the local conditions in which it lives.
eg. live oak in Austin, vs live oak in Baton Rouge
eg. flower and gardening catalogues vs local growers
still they are the same species:
they interbreed naturally where they come nto contact

18. Summary
Generally a process of natural selection, evolution sorts
through these numerous variations within a population and
“chooses” the most fit combination
as the environment slowly changes and certain variations
are selected over 100’s or 1000’s of generations new forms
will arise.

19. Reference
• https://www.khanacademy.org/science/ap-biology/natural-selection/natural-selection-ap/a/darwin-
evolution-natural-selection.
• https://www.sparknotes.com/biology/evolution/darwin/summary/#:~:text=Darwin%27s%20theory%2
0of%20evolution%2C%20also,population%20speciation%2C%20and%20natural%20selection.
• https://www.amnh.org/exhibitions/darwin/evolution-today/natural-selection-
vista#:~:text=In%20fact%2C%20it%20is%20so,%2C%20Selection%2C%20Time%20and%20Adaptation.
• https://biodiversity.ku.edu/sites/all/themes/bootstrap/bootstrap_biotheme/img/public_html/sites/all/
themes/bootstrap/bootstrap_biotheme/img/photos/schools/pdfs/Investigating_VIST_Principles.pdf
• https://biocyclopedia.com/index/general_zoology/darwins_theory_of_evolution.php#:~:text=The%20t
heories%20are%20(1)%20perpetual,and%20(5)%20natural%20selection.
• https://www.snscourseware.org/snsctnew/files/1679905244.pdf