Name:______
Date:______
Lesson # 8: Evolution
(Speciation)
Introductory Terms
-In order for one ______to become very different from another, they must be reproductively______
-This means that there will no longer be a free exchange of ______between the two populations
What is a Species?
-Includes all ______of a population that can interbreed under ______
Speciation
-Occurs when the ______of a population become split
-The formation of ______species
-The process by which reproductively isolated populations become distinct species
Modes of Speciation
-New species can form as a result of the ______of a reproductive isolating mechanism that prevents members of two populations from interbreeding
-New species can evolve under a ______of circumstances
Reproductive Isolating Mechanism
-Any behavioural, ______or biochemical trait that ______individuals of different species from reproducing successfully together
Types of Barriers
______Barriers
-A reproductive isolating mechanism that prevents______mating and fertilization
Examples
Postzygotic Barriers
-A reproductive isolating mechanism that prevents ______in ______from interspecies reproduction
1)______Isolation
-Different species use different ______ and other mating______to find and attract a mate
-Usually in the form of mating signals and ______
Examples
-Male frogs of different species have unique ______that attract only females of their own species
-Fireflies showing distinct ______of flashes attract ______mates
2) Temporal Isolation
-Different species ______at different ______of the year
Example
-Often used by ______because plants cannot move so they must use mechanisms such as ______to reproduce at specific times
One might flower in the early ______, and by the time that is done flowering another species might just beginning to flower (certain flowers mate in the spring, others in the fall)
3) Ecological Isolation
-Very similar species may occupy different ______within a region
-Species utilize different ______in the habitat
-Individuals mate in their ______habitat, and therefore do not meet individuals of other species with different ecological preferences.
Example
-The mountain bluebird lives at high ______, while the eastern bluebird prefers ______elevations and does not encounter the mountain species
4) ______Isolation
-Differences in ______features may make two species ______
-The structure of the ______is so distinct that it is often used as a character in insect classification
-Only one male reproductive organ will fit into the specific female ______tract of a species
Example
-Many insects have modifications on their genitalia such that the male and female parts are a perfect ______fit
-Orchids are shaped so that only certain beetles can reach the point of pollination, and therefor pick up the pollen. That beetle will then go to another orchid of the same type to deposit the pollen
5) Gametic Isolation
-Male gametes may not be able to ______and______an egg of a different species
-Two populations exchange sperm and egg but ______markers prevent the eggs from being fertilized because they do not recognize them
Example
-Many marine animals including corals, clams, and sea cucumbers release their sperm and eggs into open water. The sperm recognizes the eggs of their ______by chemical markers on surface of the eggs
Post Zygotic Barriers
1)Zygotic ______
-Mating and______are possible, but genetic differences result in a zygote that is unable to ______properly
-Results in______of zygote
Example
-Some species of sheep and goat are able to mate, but the zygote will die
2) Hybrid Inviability
-A hybrid individual develops but either dies ______birth or, if born alive, cannot survive to ______
Example
-When tigers and leopards are crossed, the zygote begins to develop but the p______ends in a miscarriage or stillborn offspring
3) Hybrid Infertility
-Hybrid offspring remain ______and viable but are______
Example
- Mules are the sterile hybrid offspring of a horse – donkey cross
Other Mechanisms
1)Allopatric Speciation
-The formation of a new species as a result of evolutionary changes following a period of ______isolation
Example
-River, volcano, mountain range
2) ______Speciation
-The evolution of populations within the same geographic area into ______
Example
-Various types of ______in a forest