The evolution of species

What did Darwin discover in the Galápagos Islands?

Darwin discovered plants and animals found nowhere else on Earth

What is speciation?

formation of new species

Why is speciation important in evolutionary theory?

It is important because the origin of new species is a central focus of evolutionary theory

What is microevolution?

Microevolution is change in allele frequencies in a population over time.

What does evolutionary theory explain?

It explain how new species originate and how populations evolve.

What is microevolution?

Change in allele frequencies over time

What is macro evolution

refers to broad patterns of evolutionary change above the species level

What does the biological species concept emphasize?

It emphasizes reproductive isolation

What does the word “species” mean in Latin?

It means “kind” or “appearance.

What do biologists compare when grouping organisms?

They compare morphology, physiology, biochemistry, and DNA sequences.

What is the biological species concept?

The species is a group of population that interbreed in nature and produce fertile offspring

What kind of offspring must members of the same species be able to produce?

They must produce viable, fertile offspring

What is reproductive isolation?

the existence of biological barriers that prevent two species from producing viable, fertile offspring.

What are hybrids?

Hybrids are the offspring of crosses between two different species

How can reproductive isolation be classified?

It can be classified by whether barriers act before or after fertilization

What are prezygotic barriers

Prezygotic barriers are barriers that block fertilization from occurring

How do prezygotic barriers prevent fertilization?

They prevent mating attempts, prevent successful mating, or prevent fertilization if mating occurs.

What are postzygotic barriers?

Postzygotic barriers are barriers that act after fertilization.

What do postzygotic barriers do?

They prevent the hybrid zygote from developing into a viable, fertile adult.

What is habitat isolation?

occurs when two species rarely encounter each other because they live in different habitats.

Can habitat isolation occur even without a physical barrier?

Yes, species can still be isolated if they occupy different habitats

What is temporal isolation?

occurs when species breed at different times of the day, seasons, or years

What is behavioral isolation?

occurs when differences in courtship rituals or other behaviors prevent mating.

What is mechanical isolation?

occurs when morphological differences prevent successful mating

What is gametic isolation?

occurs when the sperm of one species cannot fertilize the egg of another species.

What is reduced hybrid viability?

Reduced hybrid viability means hybrid offspring do not develop properly or survive well

What is reduced hybrid fertility?

Reduced hybrid fertility means hybrid offspring survive but are sterile

What is hybrid breakdown

first-generation hybrids may be viable and fertile, but later generations are weak or sterile

What is the difference between prezygotic and postzygotic barriers?

Prezygotic barriers prevent fertilization, while postzygotic barriers act after fertilization.

Which type of reproductive barrier occurs before fertilization?

Prezygotic barriers occur before fertilization

Which type of reproductive barrier occurs after fertilization?

Postzygotic barriers occur after fertilization

Why is the biological species concept limited

Cannot be applied to fossils or asexual organisms, including prokaryotes

What is the morphological species concept?

A species defined by physical structures or traits

What is one advantage of the morphological species concept?

It works for sexual and asexual organisms

What is the ecological species concept?

A species is defined by its ecological niche

What does the ecological species concept emphasize?

Natural selection and adaptation

What is one advantage of the ecological species concept

It applies to sexual and asexual species

What is the phylogenetic species concept

A species is the smallest group sharing a common ancestor.

What evidence is used in the phylogenetic species concept?

Morphology and molecular sequences

What is one limitation of the phylogenetic species concept?

It can be hard to decide how much difference defines a species

What are the two main types of speciation

Allopatric and sympatric speciation

What is allopatric speciation

gene flow is interrupted and reduced when a population is divided into geographically isolated from the parent population.

What is sympatric speciation?

Speciation takes place in geographically overlapped populations.

Why does dispersal ability matter in allopatric speciation?

It determines whether a barrier is effective

How do separated populations evolve in allopatric speciation?

Through mutation, natural selection, and genetic drift

How can reproductive isolation arise in allopatric speciation?

Through genetic divergence