LEC 18

1) Which is a postzygotic isolation mechanism?
Zygotic failure.

2) What is prezygotic isolation?
Barriers before fertilization.

3) What is gametic isolation?
Sperm and egg cannot fuse.

4) What is mechanical isolation?
Body parts do not fit for reproduction.

5) The BDM model explains the evolution of what type of isolation?
Postzygotic isolation.

6) Does BDM occur in allopatry or sympatry?
Allopatry.

7) What are co-adapted gene complexes?
Genes that evolved to work well together.

8) Which DNA mutates fastest?

Animal mitochondrial DNA.

9) Why does mitochondrial DNA mutate faster?
Produce free radicals (harmful), poor repair of DNA, high replication.

10) Why are mitochondria important in speciation?
They must work closely with nuclear genes.

11) What does the electron transport chain do?
Produces energy (ATP).

12) What do copepod hybrids show?
Reduced energy production (lower fitness).

13) What are cybrids?
Cells with nucleus and mitochondria from different species.

– Transplant

• nucleus of a cell from one species into the cytoplasm of the

enucleated cell of another species; or,

• mitochondria from one species into the cell of another

species.

14) What happens as species become more different?
Hybrid fitness decreases.

15) What is Muller’s ratchet?
Accumulation of harmful mutations in non-recombining DNA.

15) What is genetic rescue?
Nuclear genes adapt to fix mitochondrial problems.

16) What is the problem with BDM?
Hybrid incompatibility can be reversed by recombination.

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