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.
“Fitness”
• Result of adaptation and the struggle for existence.
• Adaptation – a heritable trait that helps the survival of an organism in
its present environment.
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.
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) by choosing which typically animal or plant males
and females will 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.
Divergent – Classifying - Cladistics
• One relatively new
system of phylogenetic
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
• Hominidae/hominini = adaptation that sets it apart is
bipedalism
• Homo habilis – 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 – using fire and tools 1.3 million years ago.
• Homo sapiens eventually evolved form a branch of this and
began replacing branches of this around the world 250,000400,000~ years ago. Over that time a gradual change in
behaviour occurred with subtle changes to societies.
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
• Some organism follow similar embryological processes.
Modern Classification
• Another feature that is considered in
classification are homologous
features, features that have similar
structure and come from similar
embryonic layers but have completely
different functions
Modern Classification
• 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.
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.
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
organisms.
• Pangaea – fossils at the top of the Rockies.
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 – 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
• 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 – ploidy {problems in cell division})
• 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.
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