New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

Chapter 24: Origins of Species

by: Amelia Notetaker

Chapter 24: Origins of Species BYS 120

Amelia Notetaker
GPA 3.88

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Chapter 24 notes.
Organismal Biology
Dr. Luciano Matzkin
Class Notes
Biology, uah, Origins, Of, species, darwin, origin, notes
25 ?




Popular in Organismal Biology

Popular in Biological Sciences

This 6 page Class Notes was uploaded by Amelia Notetaker on Tuesday December 1, 2015. The Class Notes belongs to BYS 120 at University of Alabama - Huntsville taught by Dr. Luciano Matzkin in Fall 2015. Since its upload, it has received 12 views. For similar materials see Organismal Biology in Biological Sciences at University of Alabama - Huntsville.


Reviews for Chapter 24: Origins of Species


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 12/01/15
Chapter 24 Lecture Notes • The origin of species ○ Speciation process in which one species splits into 2 or more species • What is a species? ○ Many definitions of species concepts § Biological species concept □ Species is a group of individuals that can successfully interbreed in nature and produce viable and fertile offspring ® Gene flow (mating within a species) ® No gene flow (mating between species) ○ Gene flow keeps populations together as a single species ○ Reproductive isolation: barrier that keeps species apart § Prevents formation of species hybrids in nature (gene flow) • Reproductive barriers ○ Before fertilization § Prezygotic barrier or isolation ○ After fertilization § Postzygotic barrier or isolation ○ Species can be isolated reproductively due to several isolating mechanisms • Habitat isolation ○ Species occupy different habitats, therefore they don't have the chance to mate § Insects using different plants in the same area • Temporal isolation ○ Species are reproductively active at different times, then they can't hybridize § Flowering time • Behavioral isolation ○ Different in courtship rituals will prevent hybridization § Blue-footed boobies dance • Mechanical isolation ○ Prevents successful mating § Bradybaena snails • Gametic isolation ○ Difference in egg and/sperm prevent fertilization § Sea urchins • Reduces hybrid viability ○ Fertilization occurs, but hybrid dies in development or environment § Ensating salamanders • Reduced hybrid fertility ○ Hybrid individuals are sterile § Drosophila majavensius and Drosophila arizonae • Hybrid breakdown ○ Hybrids are viable and fertile, but have a reduced or no mating success § Rice strains and lake white fish • Issues with biological species concept ○ Sometimes species can produce a fully viable and fertile offspring. How is it possible? § Grizzle and polar bear=grolar bear § Lion and tiger=liger ○ Many exceptions to biological species concept • Morphological species concept ○ Individuals with similar morphology are a single species ○ Works on sexual and asexual species but can be subjective § Which character is more important? • Ecological species concept ○ Ecology of individuals defines species § Food, shelter, physiology ○ Works on sexual and asexual species, but need to have a very clear understanding of the ecology of organisms • Phylogenetic species concept ○ Difference at genetic level defines species ○ Works on sexual and asexual species but need to defines degree of difference allowed to still be a single species • Two populations of fish are debated whether or not they are the same species or not. What would those who agree with the biological species concept do? ○ Put one population of fish in the other population's natural environment and observe if they successfully mate • Speciation ○ Ultimately occurs when two gene pools become isolated ○ Isolating mechanism describes how two species are prevented from coming back together ○ Initial separation can occur in § Allopathy § Sympathy • Sympatric speciation ○ Occurs between populations living in the same geographic area ○ How can you have divergence? § Forces splitting gene pools must be stronger than the homogenizing effect of gene flow • Allopatric speciation ○ Occurs when one population is split by a geographical feat. § The grand canyon, lake, etc • Sympatric speciation habitat differentiation ○ Shifts in resource utilization could be a strong force ○ Apple maggots (rhagoletis pomonella) § Apples introduced in 1850's ○ Created maggots that ate apples § Can mate with other fruit consuming maggots and are different, but are the same species • Sympatric speciation: sexual selection ○ Mate preference can also drive gene pools ○ Given variation in mates results in disruptive selection ○ In lake Victoria there are over 600 species in cichlids originating less than 100,000 years ago ○ Female choice based on coloration is very strong • Sympatric speciation: polyploidy ○ Very common in plants, about 80% ○ Polyploidy: occurrence in extra chromosomes due to an error in cell division ○ Rare in animals ○ Autopolyploids: when the extra set(s) of chromosomes originate from a single species ○ Allopolyploids: when extra set(s) of chromosomes originate from different species § Common with crop plants • How can a population's characteristics make allopatric speciation more possible? ○ Existing on the edge of the home range • Genetic model of speciation ○ Dobzhansky-Muller model § One population is split by a geographical feat § The now two different populations evolve and change on their own □ Mutations occur § These new genes become fixed in the two populations § Suddenly, the geographical feat is gone and the two populations attempt to mate □ They are unable to produce a viable, fertile offspring due to the differences in their mutations • Hybrid zones ○ Regions where contact between two different species produces hybrid inidividuals • Hybrid zones: case study ○ Yellow bellied toad and fire bellied toads • Presence of hybrid zone ○ Reinforcement: gets narrower and narrower until it eventually disappears § Keeps hybrids from forming ○ Fusion: 2 species become one ○ Stability: persists over time and is maintained § Maybe hybrids do better? • Reinforcement ○ Natural selection will reduce (or eliminate) the size of the hybrid zone ○ If hybrids don't perform as well as parental species, then there will be selection against creating hybrids § Reinforcing separation between species ○ Female D. megavensis from sonora weren't mating with D. drizonae males ○ Female D. megavensis from mojave will mate with D. arizonae more often • Fusion ○ If selection (reinforcement) against hybrids are week, then it's likely that the two gene pools will fuse • Stability ○ Although selection might be resent against hybrids, it's balanced by migration • Speciation rates ○ Rate of new species formation varies widely across different lineages ○ This variation in speciation rates can also be observed in fossil records • Fossil records and speciation rates ○ The fossil record can demonstrate gradual change ○ Times of punctuated equilibric • Genetics of speciation ○ Does this speciation gene exist? ○ Most speciation events are a product of change at many genes § Some have greater effect • EX: Mimulus ○ Monkey flower § Mimulus luvisii and M. cardinals ○ M.L.= bumble bees ○ M.C.=humming birds ○ Crossed two species and selected for favored color § Got M.C. to have M.L. color and vise versa ○ Flower color (one major gene) had significant effect on type of pollinator visits


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Steve Martinelli UC Los Angeles

"There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."

Allison Fischer University of Alabama

"I signed up to be an Elite Notetaker with 2 of my sorority sisters this semester. We just posted our notes weekly and were each making over $600 per month. I LOVE StudySoup!"

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.