Darwin vs.
Lamarck
Edited by : Rabab Refaat
Evolution :is how species of living
things have changed over time..
Populations of Species
Species: a group of 1 type of organisms that interbreed & are reproductively
isolated
Population: a group of a particular species living in a certain area
Whitetail Deer in the Texas
Whitetail Deer
Hill Country
Lamarck’s Theory on Evolution
(1800s)
Law of Use & Disuse: body parts got stronger or deteriorated depending on
whether it was used or not
Inheritance of Acquired Characteristics: acquired changes were passed on to
offspring
You’re naturally skinny,
but you lift weights &
become a body builder.
Your children are born
with HUGE muscles!
Lamarck’s Hypothesis
Bird ancestors wanted to fly, so Those that grew wings had
they tried until wings developed. offspring that were born
with wings.
Millions of years ago, the
ancestors of the modern
giraffe had short necks.
So, how do we explain the
evolution of the long neck?
According to Lamarck…
Giraffes’ necks grew longer from stretching for food.
The acquired trait (long necks) was passed down to offspring.
The giraffe population became long-necked.
What are your thoughts on Lamarck’s hypothesis?
Lamarck’s Hypothesis
Let’s say you have your ears pierced.
Were you born with this trait?
NO – this is an acquired trait.
According to Lamarck’s hypothesis,
your baby would be born with pierced
ears!
Lamarck’s Mistakes
Was he correct?
NO!
Traits are passed down from parent to offspring by
genes, NOT by an individual’s life experiences or
activities.
Lamarck did not know that traits were inherited
through genes!
So, HOW is life evolving?
Charles Darwin
Voyaged the world from 1831-1836
In the 19 th century.. He explained his ideas about evolution in a book
called On the Origin of Species , which was
published in 1859During his travels, Darwin collected evidence that
led him to propose a revolutionary hypothesis about the way life
changes over time.
The Theory of Evolution
In the 1800s, many scientists agreed that life on Earth had changed (& still is
changing).
◦ Jean Baptiste Lamarck & Charles Darwin were 2 of the most important evolutionary
scientists.
Darwin & Lamarck agreed that evolution was occurring – the question was
HOW?
HOW do populations of
species change over time?
Evolution
Slow, gradual change in a population over time…
… a looooooooooong time!
Today, there are 14 species
of finch that inhabit the
Galapagos Islands.
These 14 species evolved
from a single ancestor that
lived 2-3 million years ago.
finches
Seed Flower Insect
eaters eaters eaters
Tortoises
• Darwin saw differences among the giant land tortoises that inhabit the
Galapagos and learned that the tortoises varied.
• The shape of the tortoises’ shells and necks corresponds to different
habitats.
Isabela Island tortoise Hood Island tortoise
Darwin’s Theory
Survival of the fittest – or NATURAL SELECTION
Only the best adapted
(fittest) will survive!
Adaptations come
from your genes – you
are born with them.
Natural Selection is based on Darwin’s
observations and deductions
1 Organisms produce more young than the
population needs to survive.
2 There is competition between individuals for
survival.
3 There is variation between individuals.
4 Some individuals are more likely to survive and
breed than others.
Darwin’s Theory of Evolution by
Natural Selection
Variation
Overproduction
Competition
Adaptations
Darwin’s Theory of Evolution by Natural Selection
Variations
Each member of a species is genetically unique
◦ These genetic differences = differences in traits
Some variations provide an advantage in a
particular environment evolution
Darwin’s Theory of Evolution by Natural Selection
Adaptations
• Because of variations, some
organisms in a population are
better able to survive and
reproduce
• Adaptation:
▫ A phenotype that improves an
organism’s chance of survival
So, how did the long
neck evolve?
According to Darwin…
Some giraffes had short necks, but a few
giraffes were born with a random mutation
that gave them long necks.
Neck length is determined by genes.
Giraffes cannot change their genes by
stretching their necks to make them
grow.
You are born with the genes you
inherited!
According to Darwin…
The short-necked giraffes had less food to eat, so they did not survive.
The long-necked giraffes survived & reproduced & passed on the “good” genes.
Over time, what do you think What will this giraffe
happens to the short neck gene? population look like after
The long neck gene? several generations?
How does natural selection
occur?
Variation exists among This variation gives some elephants
individuals in a population. a higher chance of survival.
Some elephants are born with Elephants with large tusks are likely
longer tusks than others. to be killed by poachers.
The elephants with the
best genes will survive
better & reproduce
(high fitness).
Which elephants have
the higher fitness?
How do you think elephant populations are
changing?
Peppered Moths During the Industrial
Revolution
BEFORE
AFTER
Transitional fossils were found for intermediate
stages between ancient and modern species
Why is it incomplete ?
The fossil record is very incomplete because of :
1 ) fossils are rare , because fossilization require specific conditions.
E.g., only animals have hard body , can fossilize.
2 ) not all the fossils have been found.
3 ) dead organisms are destroyed by :
Predators ( wild animals ) ,Water damage , Climate , before they fossilize
4 ) fossils destroyed over time Thus the oldest fossils might turn to dust.
DNA
Scientists can determine if an organism is
related to another organism by
comparing their DNA.
Organisms that are close relatives have
similar DNA.
Dogs are the closest relative of bears
Genetic evidence shows that all Primates
(including us) evolved from a common
ancestor
Evolution claims:
Apes and humans descended
from a common ancestor
Evolution VS Religion
-“God created Adam on his image, This does not refer to the image of
God but the image of ADAM.
-the religion disapproves the part of the theory of evolution that say that nature
is the creator or that creatures on earth came out of random.
-Religion disapproves the part of the theory of evolution that states that human
beings evolve from a single cell and then it went up to the ape which they
call the closest relative to human being, then the human being!
-We see around us that different species learn how to adapt to different
WILL OF ALLAH
environment. But we say: that happens with the
Controversial
There are different kinds of
fossils
1-Molds and casts
2-Trace
3-Preserved remains
(whole body )
Molds and casts
A mold is a hollow area in sediment where an organism used to
be
A cast is a copy of the shape of the organism
Cast Mold
Fossil fossil
Mold Cast
Trace Fossils
Provides evidence of animal activity.
Example:
◦ Footprint / Caves
◦ Poop
Preserved Remains
(body fossils)
Some processes preserve the remains of organisms with little
or no change
◦ Tar pits
◦ Amber
◦ Freezing
What is extinct animals ?
If a species, or type, of plant or animal
dies out completely, it becomes extinct
(Dodo -Sabre-Toothed Tiger -Woolly
Mammoth)
