Download Evolution - Logan Petlak

Evolution
BI30-LE2 Examine the significance of evolution as a key unifying theme
in biology through the principles processes and patterns of biological
evolution.
Evolution – what is it?
• Key Principles
• Common misconceptions
• OpenStax Ch. 18-1 as a guiding tool or use your devices to pursue the
following information.
Key Principles and Processes of Evolution
• Descent with Modification
• Fitness as a result of adaptation and struggle for existence.
• Natural selection (need variation – genetic diversity)
• Genetic drift
• Selective breeding
• Divergent/Convergent evolution.
Descent with modification
• Over time and generations the traits providing reproductive
advantage become more common within the population.
• Our descendants become modified or changed.
• Example: if being hairy kept you warm in a constantly cold
environment, you’d be more likely to reproduce and pass on this
modification to your descendants in the population.
“Fitness”
• Result of adaptation and the struggle for existence.
• Adaptation – a heritable trait that helps the survival of an organism in
its present environment.
• Fitness does not necessarily mean strength – it could be smarts,
camouflage, or other traits that allow an organism to survive.
Natural selection
• the process whereby organisms better adapted to their environment
tend to survive and produce more offspring.
• Nature selects “for” or “against” a particular trait.
• Hair analogy in a cold environment – hair would be selected for. No
hair would be selected against.
Genetic drift
• variation in the relative frequency of
different genotypes in a small
population, owing to the chance
disappearance of particular genes as
individuals die or do not reproduce.
• Do we remember/know what a
genotype is? This can lead to the
disappearance of a particular
genotype/allele.
Selective breeding
• Selective breeding (also called artificial selection) is the process by
which humans use animal breeding and plant
breeding to selectively develop particular phenotypic traits
(characteristics). They do this by choosing a specific animal or plant
males and females to sexually reproduce and have offspring together.
• This is how GMOs are everywhere.
Divergent/Convergent Evolution
• Divergent evolution – when two species evolve in diverse directions
from a common point. Can be observed in cladistics.
• Convergent evolution – two similar traits may evolve despite a nonsimilar ancestry.
Evolution Importance
• Ultimately, all of these different aspects of evolution help us establish
potentials links and ancestry between species.
• But what’s the point of that? Why bother? What benefits could be gained?
• From studying organisms evolution, we try to classify them into similar
groups based on certain characteristics – these groups (getting more
specific) are called Kingdom, Phylum, Class, Order, Family, Genus, Species.
Divergent – Classifying - Cladistics
A particular system of phylogenetic
(genetics and traits) classification is
called cladistics.
Cladistics uses shared derived characters
to establish evolutionary relationships.
Cladistics
A shared derived character is a feature
that apparently evolved only within the
group under consideration.
Creation of a Cladogram
Make your own!
• Create a Cladogram Assignment
• Complete the front page – making a tree from the chart given.
• Create your own chart and tree on the back page. Select six
organisms and five traits that will separate them from one another.
• Which organisms are most closely related, which are least closely
related?
Why are cladograms important?
• When looking at creatures through the scope of divergent/convergent
evolution… we can begin to see organismal ancestry and how
organisms relate to one another and when certain shared derived
characteristics came into existence.
• Different types of evidence that scientists gather helps us create
cladograms and can separate some domains/species from one
another and paint a picture as to the origins of life and a Last
Universal Common Ancestor (LUCA).
Human Evolution
• https://en.wikipedia.org/wiki/Human_evolution
• Family ______________ = adaptation that sets it apart is
bipedalism
• Homo _______ (skillful human) – 2.8 million years ago. A
mutation occurred in which the SRGAP2 gene doubled – a
gene responsible for the wiring of our frontal cortex (large
part of learning)… so they started becoming bigger (more
processing power = smarter = evolutionary advantage)
• Homo _______ (upright man)– using fire and tools 1.3
million years ago.
• Homo _______ (wise human) eventually evolved form a
branch of this and began replacing branches of this around
the world _______-________~ years ago.
Over that time gradual changes in behaviour occurred
coinciding with subtle changes to societies and some
changes to our species as a whole.
Human Evolution
• https://en.wikipedia.org/wiki/Human_evolution
• Family: Hominidae/hominini = adaptation that sets it apart
is bipedalism
• Homo habilis (skillful human) – 2.8 million years ago. A
mutation occurred in which the SRGAP2 gene doubled – a
gene responsible for the wiring of our frontal cortex (large
part of learning)… so they started becoming bigger (more
processing power = smarter = evolutionary advantage)
• Homo erectus (upright human) – using fire and tools - 1.3
million years ago.
• Homo sapiens (wise human) eventually evolved form a
branch of this and began replacing branches of this around
the world 250,000-400,000~ years ago.
• Over that time gradual changes in behaviour occurred
coinciding with subtle changes to societies and some
changes to our species as a whole.
Human Evolution Theory
• _____ ___ _________ Hypothesis – small group of Homo sapiens
evolved out of Africa. _______________ ____– mitochondrial DNA is
passed from mother to offspring without recombination (apart from
mutations stays the same).
Human Evolution Theory
• Out of Africa Hypothesis – small group of Homo sapiens evolved out
of Africa. “Mitochondrial Eve” – mitochondrial DNA is passed from
mother to offspring without recombination (apart from mutations
stays the same).
Evidence for evolution
• Fossils
• Anatomy and embryology – homologous analogous structures.
• Biogeography
• Molecular biology
Fossils
• Fossil record often provides clues to
evolutionary relationships.
• The fossil record may provide the framework
of a phylogenetic tree, but a systematic
taxonomist would seek to confirm the
information it provided with other lines of
evidence.
• As we find fossils – we can infer when that
organism existed and compare its structure to
that of other fossils or existing organisms.
Anatomy (Morphology) and Embryology
• Some organisms upon comparison have homologous and analogous
structures.
• What do these terms mean?
• Some organism follow similar embryological processes.
Anatomy - Homologous
• Homologous features, features that
have similar structure and come from
similar embryonic layers but have
completely different functions
Anatomy - Analogous
• Analogous features are ones that
come from different embryological
development but look similar and
perform similar functions, like the
wings of bats and the wings of
insects.
• Which one (analogous or
homologous) connects to divergent
evolution, which one to convergent?
Embryology
• Early patterns in embryological development
provide evidence of phylogenetic relationships
• They also provide a means of testing
hypotheses about relationships that have been
developed from other lines of evidence.
• Seeing similarities in embryological
development helps us make inferences about
ancestry.
Embryology
• The fertilized egg is known as a zygote which
undergoes several cell divisions to become a
hollow ball of cells called a blastula
• A small indent on the blastula develops, this is
the blastopore.
• The order in which organisms develop in early
stages of life is a big part of classification.
• Look up phyla of organisms (just a list) – which
one do you think we’re most closely related to
and why?
Embryology
• The blastopore will develop
into an opening of the
digestive tract.
• In echinoderms and
chordates the blastopore
becomes the anus.
• In all other animals the
blastopore becomes the
mouth.
This leads to the
conclusion that
vertebrates and
echinoderms are
more closely
related.
Biogeography
• Locations of plants and animals. Similar locations  similar
adaptations required  similar organisms.
• Pangaea – marine fossils at the top of the Rockies (old glaciers).
Molecular biology
• Certain organisms share common
proteins, amino acids and segments
of DNA… observing similarities
between these in organisms help us
define how closely related they are.
Chromosomes & Macromolecules
• Taxonomists use comparisons of macromolecules such as DNA, RNA,
and proteins as a kind of “molecular clock”
• Scientists compare amino acid sequences for homologous protein
molecules of different species.
• The number of differences is a clue to how long ago two species
diverged from a shared evolutionary ancestor.
Common Misconceptions of Evolution
(Ch 18.1 will help!)
With a partner, discuss why these are wrong. You have ten minutes.
• Individuals evolve.
• Natural selection is evolution.
• Evolution is random.
• Evolution is just a theory.
• Evolution explains the origins of life.
• Organisms evolve on purpose.
Selective Pressures
Selective Pressures are
OR
Types of Pressures
•
•
•
•
•
Selective Pressures
Selective Pressures are any phenomena which alters the behavior and fitness of
living organisms within a given environment.(1)
OR
Anything that can impact the life of organisms. Puts “pressure” on organisms and
will cause selection to take place.
Types of Pressures
• Competition
• Predation
• Changes in climate
• Parasitism
• Pollution
Example of Selective Pressure
• Create an example of each selective pressure on a particular species
and what trait may help one get past this versus others in the species.
•
•
•
•
•
Competition –
Predator –
Change in climate –
Parasitism –
Pollution –
Example of Selective Pressure
• Create an example of each selective pressure on a particular species
and what trait may help one get past this versus others in the species.
• Competition – Two tigers, fightin’ over bread, stronger one lives and eats and
then can reproduce!
• Predator – Eagles are attacking rodents, porcupines who have sharper spikes
live – eagles don’t like sharp spikes.
• Change in climate – drought – Gazelle with better internal compass live.
• Parasitism – caterpillar with thicker skin – wasp can’t inject parasitic larvae
• Pollution – mammal with hairier nostrils filters out air pollutants on the way
in.
Example of Selective Pressure
• In a cold climate, animals need certain characteristics to survive, like
a warm furry coat, the ability to make burrows to live in and the
ability to collect and store food for the winter. The selective pressure
of cold weather means that animals that don't have these
characteristics and are less likely to survive and reproduce. In a hot,
dry climate, plants will have an advantage if they have phenotypes
such as the ability to store water, large root systems to absorb what
little water is in the soil, and perhaps ways to prevent water loss even
at high temperatures.
Source: Study.com
Speciation
• What is it?
• What does it involve?
• Why is it important?
Speciation
Dispersal – organisms “disperse” to new
locations
Vicariance - organisms are separated “river
divides the group”
• Involves the formation of new and distinct species in the course of
evolution. Two types: Allopatric (geographic separation of parents and the
creation of new species – dispersal and vicariance) and sympatric (parent
species is in same location but changes within population eventually lead
to new separate species – ploidy {problems in cell division})
Species – organisms able to mate with their own and have viable, fertile
offspring.
• It includes natural selection and isolation (reproductive barriers).
• It is important because these differences and changes give rise to new
species and maintain the differences between others.
Visual for Sympatric vs Allopatric Speciation
Isolation/Barriers to Reproduction
Isolation leads to ____________.
Two types of reproductive barriers prezygotic and postzygotic.
Prezygotic –
Postzygotic –
• Different barriers.
Behavioural
Temporal
Geographic
Isolation/Barriers to Reproduction
Isolation leads to Speciation. Isolation means “reproductive isolation of the
species” – what makes that species mate with itself and only itself... There
are barriers to reproduction that help this occur.
• Two types of reproductive barriers prezygotic and postzygotic.
Prezygotic - are those that prevent mating between different species.
(Gametic barriers/structural barriers).
Postzygotic - are those that reduce the likelihood that an offspring will survive
after mating has occurred, but before the offspring is actually born (can also
include sterile offspring)
Behavioural Isolation
• What is it?
• What does it involve?
• Example:
Behavioural Isolation
• Evolutionary mechanism of identifying members of same species as proper
mates.
• It involves a reproductive barrier based on behavior, usually in the form of
mating rituals and signals. Signals that attract mates to each other may be
one of the most important factors in determining whether closely related
species mate with each other or not.
• Fireflies – males flash a particular light pattern. Females only recognize that
of the same species.
Temporal Isolation
• What is it?
• What does it involve?
• Example:
Temporal Isolation
• Evolutionary mechanism that prevents species from mating because
they breed at different times. These differences can be time of day,
season, or even different years.
• It involves organisms that only mate at certain times – if the times
don’t sync up – no mating!
• Example – two similar species of frogs, but they mate at different
times of the year.
Geographic/Habitat Isolation
• What is it?
• What does it involve?
• Example:
Geographic/Habitat Isolation
• Evolutionary mechanism that refers to a
population of animals, plants, or other
organisms that are separated from
exchanging genetic material with other
organisms of the same species.
• It involves the physical separation of the
species – once isolated they begin to
evolve independently.
• Example – black cats and white cats are
separated by a new river that formed
after a flood. No more mixes… 
Evolution over Generations
• Gradualism versus punctuated equilibrium
• Divergent/convergent evolution
• Coevolution
• Adaptive radiation
• Mass extinction
• Evolutionary arms race
Gradualism
• Evolution occurs over a long period of time in small steps.
• This can happen from environmental changes. The species may not
officially change, but subtle changes/trends occur over time. (Humans
are getting taller).
Punctuated Equilibrium
• A particular species undergoes change very quickly from the parent
species and then may remain largely unchanged for an extended
period of time.
• This can happen from environmental changes.
• Stasis, change and reintroduction (snail example)
• http://evolution.berkeley.edu/evolibrary/article/side_0_0/punctuate
d_01
Gradualism vs Punctuated Evolution
Coevolution
• occurs when changes in species' genetic compositions reciprocally
affect each other's evolution.
• Can lead to exclusivity of certain plants/animals becoming dependent
on one another for survival. Evolved to live with one another.
Mass Extinction
• An extinction event (also known as a mass
extinction or biotic crisis) is a widespread and
rapid decrease in the biodiversity on Earth.
• last such extinction was 65 million years ago –
three quarters of plant and animal species were
wiped out. (Clay from this time period has lots of
iridium – uncommon on earth but common on
asteroids. With some exceptions many organisms
(tetrapods) exceeding 55 pounds did not survive.
P-Tr Extinction event. Cause – Anoxia, Meteor,
Volcanoes?
Evolutionary Arms Race
• an evolutionary arms race is
an evolutionary struggle between competing
sets of co-evolving genes, traits, or species,
that develop adaptations and counteradaptations against each other, resembling an
arms race, which could be, and often are,
described as examples of positive feedback.
• Host-parasite – virulence vs resistance.
• Adaptations and counter-adaptions (selective
pressures). Symmetrical – direct competition.
Asymmetrical – counter competition (right)
Adaptive radiation
• Adaptive radiation is the
tendency of beneficial traits
in a particular species to
radiate out from and to a
particular
location/ecological niche.
• However, when/if they
spread out, this is when we
observe similar species in
different locations that may
now be separated by
natural or man-made
boundaries.
Recent Article
• Human Evolution Update http://www.sciencemag.org/news/2016/09/almost-all-living-peopleoutside-africa-trace-back-single-migration-over-50000-years