1. Speciation

2. Speciation
Biological Species: all
members of a population
that can breed under
natural conditions and
produce fertile offspring.
(With some exceptions: there
are some animals of different
species that can have fertile
offspring)

3. Speciation
Reproductive isolating mechanism: The term given to an
obstacle that prevents inter-species breeding.

4. Think. Pair. Share.
Think of as many reasons are you can to explain why
animals of different species would be unable to breed.
Ex. Why wouldn't the following animals have offspring?
Dog and Cat
Housefly and Fruitfly
Spider and Scorpion
Raspberry and Blueberry
Salmon and Trout
Moose and deer
Cardinal and Bluejay

5. Reproductive Isolating Mechanisms
There are 2 types:
1) Prezygotic (preventing egg fertilization)
2) Postzygotic (zygote unable to reproduce)

6. Reproductive Isolating Mechanisms
1) Prezygotic isolating mechanisms include:
i) Behavioural Isolation: Differences in courtship.

7. Reproductive Isolating Mechanisms
1) Prezygotic isolating mechanisms include:
ii) Temporal Isolation: Different breeding times/seasons.
The western and eastern spotted skunks breed at
different times of the year (fall and late winter).

8. Reproductive Isolating Mechanisms
1) Prezygotic isolating mechanisms include:
iii) Ecological Isolation: Organisms have different habitats.
While similar, these
kingfishers rarely leave
their habitats for a
chance to meet the
other kingfishers.

9. Reproductive Isolating Mechanisms
1) Prezygotic isolating mechanisms include:
iv) Mechanical Isolation: Incompatible anatomies.
This beetle penis has
spikes on it - a
mechanical barrier to
reproduction with
other species.

10. Reproductive Isolating Mechanisms
1) Prezygotic isolating mechanisms include:
v) Gametic Isolation: Male gametes are unable to fertilize
the egg because they do not recognize it.
In some species the females
lay unfertilized eggs. The
male must then cover them
with its sperm.

11. Reproductive Isolating Mechanisms
2) Postzygotic isolating
mechanisms include:
i) Zygotic Mortality: The
fertilized egg can not
develop properly.

12. Reproductive Isolating Mechanisms
2) Postzygotic isolating mechanisms include:
ii) Hybrid Inviability: Hybrid organism dies before birth or
can not survive to maturity.
A leopon (lioness and
leopard) or lipard (lion and
leopardess) is sterile and has
a very short life span. None
have grown to maturity.

13. Speciation
2) Postzygotic isolating mechanisms include:
iii) Hybrid Infertility: Hybrid organism healthy but sterile.
Beefalo (domestic cow and buffalo)

14. Speciation
Speciation is the creation of a new species. The new
species evolved from an already existing species.
There are many different species of fruit flies.

15. Speciation
This may occur in 2 main ways:
1) Allopatric Speciation:
Physical separation of members of a
species will place different selective
pressures on each population.

16. Speciation
This may occur in 2 main ways:
1) Allopatric Speciation:
Different traits will be selected for survival and the
populations will evolve independent of each other.

17. Speciation
This may occur in 2 main ways:
2) Sympatric Speciation:
Species of a single population my be selected for their
extreme traits, such as colour or behaviour (disruptive
selection).

18. Speciation
This may occur in 2 main ways:
2) Sympatric Speciation:
These extreme traits become the basis for 2 different
populations with different selective pressures as they
grow apart.
The hawthorn fly species (left) gave rise to apple maggot flies
(right) , which prefer to eat apples instead of hawthorn fruits