GEN BIO 2 | Macroevolution

Darwin’s Finches

Darwin’s voyage to the Galapagos Islands led him to observe diverse groups of finches. They have various beaks depending on their island of origin and which food is available.

Macroevolution

patterns and processes associated with evolutionary change at and above the species level, often leads to speciation

Biological Species

a (group of) population whose members can interbreed and produce fertile offspring

Speciation

the formation of new species that occurs when some members of a population can no longer successfully interbreed with the rest of the group

Divergent Evolution

Interbreeding species diverge into two or more evolutionary groups due to environmental changes or migration.

Convergent Evolution

Distinctly different species become more similar in structure and function, seen in different species that live in similar environments.

Parallel Evolution

Two species that have descended from a common ancestor develop similar traits because they adapt to similar environmental changes.

Co-evolution

Occurs when one of the species changes, then the other will also change in response so the relationship can continue.

Pre-zygotic Isolation

Occurs before the formation of a zygote by preventing reproductive attempts that make it unlikely that the fertilization will be successful if mating is attempted.

Types of Pre-zygotic Isolation

1. Habitat Isolation

2. Temporal Isolation

3. Behavioral Isolation

4. Mechanical Isolation

5. Gametic Isolation

Habitat Isolation

When two species occupy different habitats even within the same geographic range, they are less likely to meet and attempt to reproduce.

Temporal Isolation

Two species can live in the same local but if they reproduce at different times of the year, they do not attempt to mate.

Behavioral Isolation

Courtship patterns that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species.

Mechanical Isolation

When animal genitalia or plant floral structures are incompatible, reproduction cannot occur.

Gametic Isolation

Even if the gametes of two different species meet, they may not fuse to a zygote.

Post-Zygotic Isolation

Occurs after the formation of a zygote, this prevents hybrid offspring from developing or breeding, even if reproduction attempts have been successful

Types of Post-Zygotic Isolation

1. Hybrid inviability

2. Hybrid sterility

3. Hybrid breakdown

Hybrid Inviability

The genes of different parent species may interact in ways that impair the hybrid’s development or survival in its environment.

Hybrid Sterility

The zygote can develop into a sterile adult, but if the chromosomes of the parent species different number or structure, meiosis in the hybrids may fail to produce normal gametes.

Hybrid Breakdown

Some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species offspring of the next generation are feeble or sterile.

Modes of Speciation

the different ways speciation occurs

Allopatric Speciation

A new species forms when a geographical barrier physically separates a population into two that cannot interbreed.

Parapatric Speciation

Occurs when two population live in neighboring areas but share a border zone.

Sympatric Speciation

A population develops into two or more reproductive isolated groups without prior geographic isolation.