What is evolution? Explain what you
know.
EXPLORING CHANGE OVER TIME
HOW DID ORGANISMS EVOLVE?
Evolution is the change in heritable traits
through generations • CHANGE OVER TIME
• Occurs in populations, not individual organisms
At the time life emerged on earth (about
3.8 billion years ago), the atmosphere is
thought to have contained very little
oxygen! • First cells were thought to be anaerobic
• Recall that “anaerobic” means “without oxygen”
As the atmosphere of the Earth changed,
so did the development of organisms
These prokaryotic (simple), anaerobic
cells were able to exist in Earth’s early
atmosphere
As Earth’s atmosphere and conditions
changed, photosynthetic prokaryotes
evolved, using sunlight to produce food • What molecule do photosynthetic organisms
produce as byproduct (waste)?
Eventually, Earth’s atmosphere became
filled with oxygen • Aerobic organisms evolved
This resulted in the evolution of
eukaryotic complex multicellular
organisms we have on Earth today!
The endosymbiotic theory proposes that
eukaryotic cells arose from living communities
formed by prokaryotic organisms.
~2 billion years ago: • Evolution of internal membranes in prokaryotes The result was the ancestor of all eukaryotic cells.
Endosymbiotic theory: Eukaryotic cells formed from a symbiotic relationship among several different prokaryotic organisms • Prokaryotes that use oxygen to generate energy-rich
molecules of ATP evolved into mitochondria.
• Prokaryotes that carried out photosynthesis evolved into chloroplasts.
Fossils show us the similarities between
organisms of the past and present
220 Million Years Ago 190 Million Years Ago Today
Homologies describe similarities
between the anatomical structures of
species
Vestigial structures are anatomical
structures that still appear, but are no
longer used! • Examples: Tails in humans, legs in snakes
• Suggests that these structures may have existed
at a previous time or in an ancestor; organisms
evolved and structures not needed
Insects and animals often have very similar embryonic development • Ex. All
vertebrates (have a backbone) have similar development
• Suggests a common ancestor
Comparison of DNA and macromolecules
between organisms • Through gel electrophoresis
• Tells us what organisms are closely related
1. Explain how cells are thought to have
evolved over time.
2. What are the different piece of evidence
we have for evolution?
Moth
Bird wing
Type of Evidence?
baby elephant
in womb
1-2 feet long
OSTRICH
EMU
SURVIVAL OF THE FITTEST
Charles Darwin is best known for his contributions to the theory of Evolution
On a five year voyage on a ship called the Beagle, Darwin recorded his observations of organisms and fossils he found along the way
This led Darwin to develop the idea of evolution and natural selection
“Survival of the Fittest” means that those
organisms best adapted to their environment
will survive, reproduce, and pass on genes
• “Fittest” means best adapted, not strongest!
Any heritable trait an organism has that
helps it to survive
What are some adaptations of this falcon?
If an organism does not have adaptations
to best fit its environment, it will die
“Survival of the Fittest” • Example: Bird beaks-Imagine that birds had
different sized beaks in an area where the food
source was seeds. In order to crack them, the
birds needed a large, strong beak. Which would
survive and reproduce?
Species have the potential to increase exponentially, but environmental factors maintain lower population numbers • Resources required to sustain life • Environmental conditions • Relationships among organisms in food web
Changing environments select for specific phenotypes • Those organisms with favorable adaptations survive,
reproduce, and pass on their alleles to future generation
• Over time, the accumulation of favored alleles leads to a change in species (change over time = evolution)
Organisms are constantly changing and adapting; bacteria reproduce and evolve quickly to adapt to constant changes!
Humans often use antibiotics to combat harmful bacteria (ex. Staphylococcus)
Some bacteria are born with a natural resistance (an adaptation!) to the antibiotic
These bacteria will survive and reproduce, creating a group that are resistant to the drugs
Pesticide Resistance in Plants Antivirals Passive Immunity: Immunity to certain
diseases is given from mother to baby at birth • Continued through antibodies passed through
breastmilk Active Immunity: Immunity acquired
through exposure to a disease • After exposure, your body builds up an immunity • Vaccines allow you to artificially gain an active
immunity without exposure to the actual disease
Genetic Recombination • Dominant and Recessive alleles in genes, along
with polygenetic traits and complex genetics,
lead to individual organisms with different
phenotypes (and thus, adaptations)
Mutations • Changes in DNA sequences can introduce both
good and bad new traits into a population
(ex. Immunities, resistant bacteria, pesticide
resistant plants)
What does it mean to be the “fittest” individual?
Which moth has the greatest chance for survival? Why?
Over time as natural selection occurs and the moths that survive go on to reproduce, what color will be most common in the population?
HOW SPECIES CHANGE OVER TIME
Speciation refers to the evolutionary
process by which new biological species
arise
When one extreme phenotype has the
best chance to survive
As a result, the frequency (number) of
those with that phenotype shift over time
Woodpecker beaks
DIRECTIONAL
selection
Using the diagram
as evidence, how did
the horse evolve
over time?
Hypothesize why
these changes could
have happened.
When the intermediate phenotype has
the best chance to survive • Heterozygote
advantage
• Birth weight
When both extreme phenotypes have the
best chance to survive • Peppered moth
Decide if the following scenarios are directional, stabilizing, or disruptive selection. • In a population of green, white, and brown
grasshoppers, the green often survive due to their body color matching the grass. Brown and white are often preyed upon by predators.
• In mollusks, white and black mollusks survive well at different levels of water. Grey mollusks are a target for predators.
• In human babies, small and large babies bring complications at birth. As a result, most babies are born in the 6-8 pound range.
HOW SPECIES CHANGE OVER TIME
When mountains, islands, etc. keep a
population isolated
Species will meet different environmental
challenges, change and evolve independently
than the original population
Lemurs of
Madegascar
Differences in phenotype within one gene • Example: Eye color in humans
• Brown eyes are naturally protected from the sun’s
glare
When one species evolves due to a
specific interaction with another species • Example: Flowers and birds/insects; flowers
pollinated by hummingbirds often have a
narrow, tubular shape
The change in a frequency of a gene variant (allele) in a population due to random chance • Due to a random event, a
significant change happens to the organisms in a population
• Much more frequent is small populations!
• Example: Founder Effect
Bottleneck Effect
1. What is survival of the fittest? How does this fit into the idea of natural selection?
2. What would occur over time if you had a group of organisms who were separated by a river?
3. Sometimes, natural selection does not play out how we expect. What is it called when selection takes place due to random chance?
CLASSIFYING ORGANISMS
Classification systems are how we
organize organisms
This is called taxonomy
The classification of organisms has
changed and evolved over the years due
to new knowledge • Greater understanding of evolutionary
relationships, thanks to DNA technology, has
allowed for more detailed classification
The classification of organisms begins with the largest groupings and moves down to the smallest (domain species)
The classification order is as follows: • Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
Easy way to remember: King
Phillip Came Over For
Grandma’s Spaghetti!!!
Group of the same organisms • Live together
• Mate and produce viable offspring
“Viable” means they can have babies of their own
The scientific name of an organism is the
Genus and Species of an organism • Always written in italics
• Example: Humans are Homo Sapians
Only species are able to interbreed!
Only species are able to interbreed. Organisms of two different species normally will not breed
Sometimes, organisms within the same genus are able to interbreed, but the offspring are not viable (they cannot reproduce!) • Example: Mules; Ligers
• These hybrid organisms are much more common in captivity than in the wild
1. What is the scientific name for
humans?
2. What components make up the
scientific name?
3. What classifies a species?
A key that helps identify an organism
Uses questions to lead you to the
scientific name of an organism • By looking at features of an organism, the key
will help you determine what it is!
1. Organisms are classified into 7 major groups. List these groups in order from largest to smallest.
2. Which is the best description of how natural selection changes a species over time?
a) Survival of the strongest organisms in an environment
b) Elimination of the smallest organisms by largest organisms
c) Survival of the organisms genetically best adapted to the environment
d) Survival of the organisms that occupy the largest area in an environment
Shows the evolutionary relationship between
organisms
Can show which organisms are more closely
related than other organisms
Which organism is
more closely related
to man? __________
Which organism is
man more closely
related to: Frog or
bird? Why?
Shows relationships up-close;
characteristics they share
1. Which two organisms are most closely
related?
2. What trait do lizards have that salamanders
don’t?
A. Evolution is survival of the smartest
B. Evolution is survival of the strongest
C. Evolution is survival of the fittest
D. Evolution is survival by luck
The forelimbs of whales, dogs, humans,
and bats are all similar in their
arrangement and structure. What
category of evidence is exemplified? a) Fossils
b) anatomical similarities
c) biochemical comparison
d) embryological comparison
a) Organs
b) Adaptations
c) Natural Selection
d) Vestigial Structures
a) It doesn’t exist
b) It can reproduce and have offspring
c) It’s parents are not the same
d) It cannot reproduce and have babies of
its own
a) Variation
b) Natural Selection
c) Isolation
d) Speciation
How does pesticide resistance in insects lead to the evolution of the overall insect species? a) The species will develop different eating methods
to avoid the pesticides
b) Insects surviving pesticide applications become weaker and will eventually die
c) Farmers will use different pesticides to kill the insects, eliminating the species
d) Pesticide-resistant insects will survive and reproduce, increasing the percentage of pesticide-resistant insects in the population
Which immune response is passed from
mother to child through breast feeding? a) Active
b) Passive
c) Humoral
d) Cell-mediated
Natural selection cannot occur without
a) competition for unlimited resources.
b) gradual warming of Earth.
c) genetic variation in species.
d) asexual reproduction in species.
The classification of some organisms has changed. Which new process is used to reclassify organisms? a) Organisms are now given Latin-based
scientific names
b) Structures are now examined at the molecular level
c) Organisms are now divided into three kingdoms
d) Structures are now used to classify organisms
Define the following terms: • Fitness
• Natural Selection
• Speciation
• Genetic Drift
• Species
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You have a test today! Take 10 minutes to study: • Evidence of Evolution
• Darwin’s Theory of Evolution
• Types of Selection
• Speciation
• Dichotomous Keys
• Phylogenetic Trees
• Classification: REMEMBER-King Phillip Came Over For Grandma’s Spaghetti!