SBI3U
Ms. Girvan
ADAPTATIONS & SPECIATION
I. Adaptation:
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_________________________________________________________________________________
_________________________________________
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A product of natural selection
Organisms become adapted to their environment over a period of time
through natural selection
Variations within a species are the raw material upon which natural selection
acts
Types of Adaptations:
1. Structural – physical features on an organism
Examples:________________________________________________
2. Physiological - associated with functions in organisms
Examples: _______________________________________________
3. Behavioural - how organisms responds to their environment
Examples: ________________________________________________
II. How Species Form:
Scientist must consider the following when distinguishing one species from
another:
- ____________________________________
- ____________________________________
- ____________________________________
- ____________________________________
Biological Species Concept
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SBI3U
Ms. Girvan
Most common definition of species:
- A species consists of a ______________________ compatible population
- A population that can interbreed and produce viable and fertile offspring
- Note: Not always possible to apply this definition
Forming a New Species:
Speciation: formation of a new species from an _____________________________
 Macroevolution
Two general pathways:
1. Transformation
- Results from accumulated changes over long periods of time such that
one species is transformed into another
2. Divergent Speciation
- One or more species arise from a parent species that continues to exist
- Promotes biological diversity (increases number of species)
Barriers to Reproduction:
1. Geographical Barriers
- Keeps populations physically separated
- Ex. Rivers
2. Biological Barriers
- Keeps species reproductively isolated when their habitats overlap
- May be pre-zygotic or post-zygotic barriers
Pre-zygotic Barriers – Prevent mating or fertilization:
1. Habitat Isolation:
- Populations live in _______________________________________
- Ex – mountains vs lowlands.
2. Behavioural Isolation:
- __________________________ behaviors different.
- Different sexual attractions operating.
- Ex – songs and dances in birds.
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SBI3U
Ms. Girvan
3. Temporal Isolation:
- __________________________________________________________Ex – flowers open
in morning or evening.
4. Mechanical Isolation:
- __________________________________________________________
- Ex – anthers not positioned to put pollen on a bee, but will put pollen on
a bird.
5. Gametic Isolation:
- __________________________________________________________
- Ex – chemical markers on egg and sperm fail to match.
- Separates certain closely related species of aquatic snails
Post – Zygotic Barriers – Prevent hybrid zygote from developing
into a healthy fertile adult
1. Hybrid Inviability
- __________________________________________________________
- Ex. Hybrid from sheep and goat die in early development
2. Hybrid Sterility
- __________________________________________________________
- Ex. Horse + Donkey = Mule
3. Hybrid Breakdown
- __________________________________________________________
- When hybrids mate the offspring of the next generation are sterile or
weak
- Ex. Cotton
Types of Speciation
1. Allopatric Speciation
- When a population is ________________ into two or more isolated groups
by a _______________________________________
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SBI3U
Ms. Girvan
- Sometimes called geographical speciation
- Eventually the groups will become so distinct that interbreeding will be
impossible
- Isolation does not need to be indefinite, but it does need to be long
enough for population to become reproductively incompatible
- Ex. Glacier, lava flow, ocean levels
Allopatric Speciation cont…
Adaptive Radiation:
- This is a form of _____________________ speciation where a common
ancestral species diversifies into a variety of differently adapted species
- Ex. Darwin’s Finches
II. Sympatric Speciation
- When populations live in the _______________ geographical area become
reproductively ________________________
- More common in plants than animals
- Speciation can occur in 1 generation if genetic change results from
parent to offspring
- Ex. Extra chromosome (called __________________) usually in plants which
can self pollinate
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SBI3U
Ms. Girvan
Convergent vs. Divergent Evolution:
Divergent Evolution –
Convergent Evolution –
Gradualism vs. Punctuated Equilibrium
Gradualism –
Punctuated Equilibrium –
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