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 Selection when specific organisms of a species are

bread to emphasize/enhance certain traits breeds of dogs

Natural Selection when certain traits are propagated in a

population due to their ability to increase survival and reproductive ability Darwin’s Finches

ARTIFICIAL SELECTIONADVANTAGES & 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

healthhttp://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 Microevolution1. Natural Selection (including Sexual Selection)2. Artificial Selection/ Selective Breeding3. Genetic Drift- The Bottleneck Effect4. Genetic Drift - The Founder Effect5. Gene Flow6. 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=ATWE2Y5uOMw

http://www.youtube.com/watch?v=YCoEiLOV8jc

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

Ontario variety is tetraploid (4n) while Cope variety is diploid (2n)

Orange day lily is triploid (3n) and produces 3x as many petals as diploid varieties

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 membrane-

bound 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)

Cladogram• Cladogram: A phylogenetic diagram that

specifies the derived characters of clades.

http://www.youtube.com/watch?v=46L_2RI1k3k

How to Draw a Cladogram

Spine Legs Hair Opposable Thumbs # of derived traitsWorm - - - - Fish + - - -

Toad + + - -

Lion + + + - Human + + + +

•Identify the “outgroup” that has no derived traits. •Use the number of derived traits (from lowest to highest) to help create your cladogram.

http://www.youtube.com/watch?v=ouZ9zEkxGWg

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