Question

1. The four species concepts discussed in class are: explain them, be able to identify examples, describe when they would be used, and identify their shortcomings.

2. Know which one Darwin subscribed to and the importance of Ernst Mayr's work.

3. Explain what we mean by 'hybrid.'

4. Explain the term 'Reproductive Isolation.'

5. Pre- and Post-Zygotic Isolating Mechanisms: Explain them and be able to identify examples of them.

Answer 1

1. The four species concepts discussed in biology are the Biological Species Concept, the Morphological Species Concept, the Ecological Species Concept, and the Phylogenetic Species Concept.

- **Biological Species Concept:** This concept defines a species as a group of organisms that can interbreed and produce fertile offspring. It is primarily based on reproductive isolation. Example: Lions and tigers are considered different species because they produce infertile offspring (ligers) when they interbreed. Shortcoming: It doesn't apply to asexual organisms and is challenging to apply to fossils.

- **Morphological Species Concept:** This concept defines species based on physical characteristics and similarities in appearance. It is useful for identifying species when information on mating is unavailable. Example: Different types of finches in the Galápagos Islands. Shortcoming: It may not account for hidden genetic variation.

- **Ecological Species Concept:** This concept defines species by their ecological niche or role in an ecosystem. It focuses on the ecological relationships between organisms. Example: Two bird species that occupy different niches in the same forest. Shortcoming: It may not apply to cases where niches overlap.

- **Phylogenetic Species Concept:** This concept defines species based on their evolutionary history and genetic relationships. It considers common ancestry and genetic divergence. Example: Identifying species by analyzing DNA sequences. Shortcoming: It may require extensive genetic data and is not always practical.

2. Darwin subscribed to the Biological Species Concept. Ernst Mayr's work was important because he helped develop and popularize this concept, emphasizing the role of reproductive isolation in defining species.

3. A 'hybrid' is the offspring resulting from the mating or reproduction between two individuals of different species or genetically distinct populations.

4. 'Reproductive Isolation' refers to mechanisms or barriers that prevent members of different species from interbreeding and producing fertile offspring. These mechanisms maintain species integrity. Examples include geographical isolation, behavioral differences, or genetic incompatibility.

5.
- **Pre-Zygotic Isolating Mechanisms:** These mechanisms prevent the formation of a zygote (fertilized egg). Examples include habitat isolation (species occupy different habitats), temporal isolation (species breed at different times), behavioral isolation (species have different courtship rituals), mechanical isolation (anatomical differences prevent mating), and gametic isolation (sperm and egg are incompatible).

- **Post-Zygotic Isolating Mechanisms:** These mechanisms occur after fertilization and prevent hybrid offspring from developing or reproducing. Examples include reduced hybrid viability (hybrid offspring have low survival rates), reduced hybrid fertility (hybrid offspring are sterile), and hybrid breakdown (first-generation hybrids are viable, but their offspring are feeble or sterile).

Answer 2

1. The four species concepts:

- Biological: based on interbreeding and fertile offspring

- Morphological: based on physical traits

- Ecological: based on ecological niche

- Phylogenetic: based on genetic relationships

2. Darwin and Ernst Mayr: Darwin supported the biological species concept, while Mayr further studied it.

3. 'Hybrid': offspring from different species or subspecies.

4. 'Reproductive isolation': mechanisms preventing interbreeding.

5. Pre- and post-zygotic isolating mechanisms: prevent successful reproduction.

- Pre-zygotic: temporal, behavioral, mechanical barriers.

- Post-zygotic: hybrid inviability, sterility.

Examples:

- Pre-zygotic: different mating calls in frogs.

- Post-zygotic: mule produced by horse and donkey, but infertile.

In summary, these concepts explain species boundaries, speciation, and mechanisms preventing successful reproduction.