Transcript Exam Review - Evolution

EVOLUTION EXAM REVIEW
SPECIES AND POPULATIONS

Species
a group of organisms
 mating between members of the group occurs
naturally
 offspring are healthy and fertile


Populations
a group of individuals of the same species that live in
a particular area
 mating occurs between members of the same
population

GENETIC VARIATION
caused by differences in the genetic code of
individuals
 lots of variation allows for higher success



success in biology is described as the ability of a
species to survive and produce healthy offspring
sources of variation include mutations and
recombination (synapsis/crossing over)
http://www.dnalc.org/view/15117-Genetic-variations-in-humans-Kenneth-Kidd.html
http://www.dnatube.com/video/685/DNA--Duplication-and-Mutations
NATURE AND ARTIFICIAL SELECTION
 Artificial

when specific organisms of a species are
bread to emphasize/enhance certain traits

breeds of dogs
 Natural

Selection
Selection
when certain traits are propagated in a
population due to their ability to increase
survival and reproductive ability

Darwin’s Finches
ARTIFICIAL SELECTION
ADVANTAGES & DISADVANTAGES

Advantages






increased food production
increase in quality of food
domestication
pets with “desirable traits”
creation of new species
Disadvantages
reduced genetic variation
 loss of biodiversity
 “desirable traits” can cause reduced fertility and
health

http://www.youtube.com/watch?v=bi9Pa0DHG5Y
http://www.youtube.com/watch?v=i7kbPsCdyQ0
Important Terms & Concepts
• Gene pool: consists of all the alleles in all the
individuals that make up a population
• Sources of variation:
1. Mutation of DNA sequence
2. Sexual reproduction
- crossing over/ random assortment
Important Terms & Concepts
• Changes to Gene Pools
– Measured using Hardy-Weinberg equilibrium
– Equilibrium of a gene pool means it is not evolving
and the frequencies of alleles are constant
– Equilibrium will be maintained if:
•
•
•
•
•
Must be random mating
Large population
No movement in or out of the population
No mutations
No natural selection
Types of Evolution
• Evolution depends on the selection of favorable
traits
• Several factors may disrupt the Hardy-Weinberg
equilibrium, and therefore cause microevolution
• Types of Evolution:
– Microevolution – Changes within a population
– Macroevolution – The origin of new species (aka
“speciation”)
Mechanisms of Microevolution
1. Natural Selection (including Sexual Selection)
2. Artificial Selection/ Selective Breeding
3. Genetic Drift- The Bottleneck Effect
4. Genetic Drift - The Founder Effect
5. Gene Flow
6. Human Influence
Group Activity
- using your notes from Friday, or provided notes,
write a point form note on the board and teach the
concept to the class
Homework p.223 #10, 11, 12, 16
Recall: Types of Evolution
• Microevolution – changes
within a population of a
particular species
• Macroevolution – changes
that produce entirely new
species = speciation
– Speciation is evident in the
fossil record and can lead to an
increase in biodiversity on
Earth
Allopatric Speciation
• Speciation caused by geographic isolation
1) Great distance between populations
• Ancestors migrate to different islands (Galapagos
finches)
Allopatric Speciation (cont)
2) Physical barrier between populations
• Isthmus of Panama divides Pacific Ocean and
Caribbean Sea
• Formation of Rocky Mountains created
different environmental conditions on either
side
• Human influence
http://www.youtube.com/watch?v=YCoEiLOV8jc
http://www.youtube.com/watch?v=ATWE2Y5uOMw
Sympatric Speciation
• A new species evolves within a large
population; the new species coexist in the
same environment.
1) Gradual: Due to changes in behaviour
• Hawthorn flies vs Apple Flies
Sympatric Speciation (cont)
2) Sudden: Due to mutation or polyploidy
• Polyploidy – organisms of the same species with
different numbers of chromosomes (2n, 4n, etc.)
• Ontario’s eastern gray treefrog and Cope’s gray treefrog
Orange day lily is triploid (3n) and
produces 3x as many petals as
diploid varieties
Ontario variety is tetraploid (4n) while
Cope variety is diploid (2n)
Patterns in Evolution
• Natural selection leads to many predictable
outcomes
• On a grander scale, these predictable
outcomes produce recognizable patterns in
evolution
(A) Divergent Evolution
(B) Convergent Evolution
(C) Coevolution
Divergent Evolution
• Divergent evolution is also called adaptive
radiation
• A common ancestor gives rise to many
different species that each fill a different
ecological niche.
– Niche: All factors related to the role of an
organism in the environment (predators, prey,
habitat, nocturnal/diurnal, etc)
Divergent Evolution (cont)
• Examples:
– Ontario rodents
– Galapagos finches
Convergent Evolution
• Different species that do not share a recent common
ancestor have evolved similar traits because they
experience the same selective pressures (analogous
features)
Ex. 1 Eyes of spiders and
humans
Ex. 2 Streamlined body shape
of sharks and dolphins
Coevolution
• Two species evolve simultaneously when the survival
of one species is influenced by the other
• Examples:
– Predator-Prey: “evolutionary arms race”
– Flowering plants and pollinators
– Species that rely on mimicry for survival will continue to
evolve if the species they mimic changes
How Did Life Begin?
• Abiogenesis – The first living things arose
from non-living matter
– Theory initially proposed independently by two
different scientists in 1920’s
– Suggested that first life forms arose spontaneously
once the first organic molecules were made in
“primordial soup”
*Organic compounds include carbohydrates, fats, protein,
and DNA, and are the building blocks of all living things
Young Earth Conditions
• Geologic evidence suggests that
the atmosphere contained carbon
monoxide, carbon dioxide,
nitrogen, methane, hydrogen,
ammonia, hydrogen sulfide, and
water vapor (but little or no
oxygen)
– Oxygen is very reactive
• Energy from volcanic eruptions,
lightning, and UV radiation would
be more intense than they are
today
First Cells on Earth
• Prokaryotes: cells that do not have membranebound organelles
– Heterotrophs: feed on other cells
– Chemoautotrophs: Make their own food from simple
inorganic molecules (without light)
– Photosynthetic: Make their own food from carbon
dioxide and light (produce oxygen)
• Oxygen would have been toxic,
– some cells adapted to survive in O2
– adapted further to using the oxygen for respiration as it
accumulated in the atmosphere (aerobic prokaryotes)
Origin of Eukaryotic Cells
• Eukaryotic cells have membrane-bound
organelles (including the nucleus)
– Believed to have evolved from prokaryotes by inward
folding of cell membrane
– Early eukaryotes did not contain mitochondria or
chloroplasts
• Endosymbiotic theory: Explains the origin of
chloroplasts and mitochondria:
– Early eukaryotes ingested aerobic prokayotes, but
were not digested; established “symbiotic
relationship”
– Led to vast increase in multicellular organisms
Cladistics
• Cladistics: The process used to
determine the sequence of
branches in a phylogenetic tree
• Each branch of a phylogenetic tree
is called a clade; it consists of an
ancestral species and all of its
descendants
– Clades can nest within larger clades
– A clade may represent an individual
species, genus, or family.
– All members of a clade must share a
homologous feature that does not
exist outside of the clade = derived
characters (= synapomorphy)
http://www.youtube.com/watch?v=46L_2RI1k3k
Cladogram
• Cladogram: A phylogenetic diagram that
specifies the derived characters of clades.
http://www.youtube.com/watch?v=ouZ9zEkxGWg
How to Draw a Cladogram
•Identify the “outgroup” that has no derived traits.
•Use the number of derived traits (from lowest to highest) to help create
your cladogram.
Worm
Fish
Toad
Lion
Human
Spine
+
+
+
+
Legs
+
+
+
Hair
+
+
Opposable Thumbs # of derived traits
+
What derived traits make humans
unique? Structural Differences
• Hairlessness
• Skeletal structure
– Skull
• Larger Brain Case
• Less protruding mandible
• Position of foramen
magnum
– Pelvis: Wider & shorter
– Spine: Lumbar curve
What derived traits make humans
unique? Cognitive Differences
• Ability to perform
complex reasoning and
exceptional ability to
learn
– Linked to longer
childhoods
• Communicate using
complex language
– Lower position of voice
box enables speech
Exam Review – Evolution
Topics:
• Species, Genetic Variation & Selection – natural selection & artificial
selection
• Mechanisms of Evolution – Hardy Weinberg equilibrium, genetic drift, gene
flow
• Microevolution vs macroevolution
• Speciation – allopatric, sympatric
• Patterns of evolution – convergent, divergent, co-evolution
• Origin of Life – abiogenesis, endosymbiosis
• Cladistics – create a cladogram p. 483-483
• Human Evolution – characteristics of humans vs other primates/hominids
Review Questions:
• Evolution unit not in normal textbook – create your own notes and review
homework questions
• OR – sign out the other textbook