WHAT IS
EVOLUTION?
Evolving --> changing
Changes accumulated over time
Did the giraffes neck evolve to be long, so that the giraffe could
reach the high branches?
Did you evolve from a chimp?
Why aren’t humans still evolving from chimps?
WHAT IS
EVOLUTION?
DEFINITION
EVOLUTION IS A PROCESS THAT RESULTS IN CHANGES IN THE GENETIC MATERIAL OF A POPULATION OVER TIME
EVOLUTION REFLECTS THE ADAPTATIONS OF ORGANISMS TO THEIR CHANGING ENVIRONMENTS AND CAN
RESULT IN ALTERED GENES, NOVEL TRAITS AND NEW SPECIES
WHAT IS EVOLUTION?
WHAT IS EVOLUTION?
MUTATIONS
MECHANISMS OF
EVOLUTION
NATURAL SELECTION
GENETIC DRIFT
= Mechanisms that lead to changes in a population
POPULATION = group of interacting organisms
(same species, same time, same place)
These mechanisms change the allele frequency
from one generation to another
ALLELE = different variations of the same gene
GENE FLOW
MUTATIONS
CREATE VARIATIONS
MUTATION = changes in DNA, that is inherited
If the change isn’t passed down to an offspring, it is not a mutation,
so it has to happen in an egg cell or a sperm cell (reproductive
cells)
When variations are created, natural selection has something to
select from!
Mutations create new phenotypes, and they can be more
equipped to survive in the given environment
Who’s DNA mutates faster?
population of bacteria or population of elephants
What does it mean to be lactose – intolerant?
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TYPES OF MUTATIONS
MUTATION ARE THE ONLY MECHANISMS THAT CAN CREATE
VARIATIONS - NEW ALLELES
MUTATION CAN AFFECT LARGER PART OF THE GENOME
(WHOLE CHROMOSOMES) OR ONLY ONE NUCTEOTIDE
POINT MUTATIONS - WHEN ONLY ONE NUCLEOTIDE BASE IS
CHANGED (PICTURE -->)
for example - sickle cell anemia
MUTATIONS ARE NOT ALWAYS BAD!
The changes can be benefitial or bad depending on the
environmant
One mutation can at the same time be good for one habitat, but
bad for a different one
Some mutation can be SILENT - meaning they do not cause a
chanhe in the amino acid sequence of the protein
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GENETIC DRIFT
CAUSES CHANGES BY CHANCE ALONE
Changes in the allele frequency occur totaly random
Bottleneck effect – allele frequency changes because
portion of alleles is lost randomly (it doesn’t reflect how
well adapted the organisms were)
Bottleneck
effect
Genetic drift occurs when the alleles that make it into the
next generationin the population are a random sample of
alleles currently present in the population
They do not have to be an accurate representation of the
current allele frequency
Founder effect - when a small group of individual
seperate from the original population and they start a new
colony, this new population will have a radnom selection
of alleles and will probably be less diverse
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NATURAL SELECTION
WHO GETS EATEN,
WHO GETS TO REPRODUCE?
Natural selection is the pressure that environment
exerts on a population
The stronger the pressure, the fewer individuals
survive
VARIATIONS = differences
There has to be variation for natural selection to
have something to chose from
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NATURAL SELECTION
STABILIZES, DIRECTS OR DISRUPTS?
STABILISING – average phenotype
survives most
DIRECTIONAL – one of the extremes
survives
DISRUPTIVE – average phenotype is
eliminated, but both extremes are well
adapted to the environment
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GENE FLOW
THERE WERE NONE, NOW CAME ONE
Gene flow happens when organisms or their
reproductive cells (pollen) migrate into a different
population and reproduce there
This makes the population more diverse – new
genes
But,
The two populations are now more alike – same
genes
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SPECIATION
CREATION OF A NEW SPECIES
Where does a new species come from?
What is a species?
SPECIATION
Single species branch into two or more new
species
They become so different, that they can’t
reproduce
REPRODUCTIVE ISOLATION
Why does it happen?
ALLOPATRIC – physical barrier (geographic
separation) between populations
SYMPATRIC – they stay in the
same location, but some
changes in their genetic material (DNA)
make it impossible for them to reproduce
and make fertile offspring
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YOUTUBE
WHAT IS EVOLUTION? - https://youtu.be/GhHOjC4oxh8
ALLELES & GENES https://www.youtube.com/watch?v=pv3Kj0UjiLE
GENETIC DRIFT https://www.youtube.com/watch?v=W0TM4LQmoZY
NATURAL SELECTION & ANTIBIOTICS (MUST WATCH)
https://www.youtube.com/watch?v=7VM9YxmULuo
THANK YOU!
KATARINA RADAKOVIĆ
katarina98.radakovic@gmail.com
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