Speciation and extinction

What is macroevolution?

Scale evolutionary change that includes speciation events.

According to the biological species concept, how is a species defined?

A species is a population or group of populations whose members interbreed and produce fertile offspring.

What triggers speciation according to the biological species concept?

Speciation occurs when some members of a population can no longer successfully interbreed with the rest of the group.

What are some limitations of the biological species concept?

It does not apply to asexual reproducing organisms, cannot be applied to extinct animals, and some organisms can interbreed in captivity but not in nature.

What is a prezygotic reproductive barrier?

A barrier that prevents the formation of a zygote, leading to separation of species.

What is habitat isolation?

A prezygotic barrier where different species occupy different environments, such as ladybugs occupying different types of plants.

What is temporal isolation?

A prezygotic barrier where species are active or fertile at different times, like field crickets maturing at different times.

What is behavioral isolation?

A prezygotic barrier where different species have different courtship activities, such as frogs having differing mating calls.

What are the three basic steps of speciation?

1. Physical division of a population. 2. Each portion follows its own evolutionary path. 3. Accumulation of genetic differences leads to reproductive barriers.

What is the significance of reproductive barriers in speciation?

Reproductive barriers prevent interbreeding between populations, allowing speciation to occur.

What is the role of microevolution in macroevolution?

Microevolution involves small changes in a population that accumulate over time, leading to larger-scale macroevolution.

Why is the biological species concept not applicable to all organisms?

It cannot be applied to asexual organisms, extinct species, and situations where interbreeding is possible only in captivity.

What is the importance of fertile offspring in defining a species?

Fertile offspring are essential for maintaining the gene pool and defining species according to the biological species concept.

How can closely related species produce fertile offspring despite separate gene pools?

Some closely related species can interbreed and produce fertile offspring, even though their gene pools remain mostly separate.

What question arises when determining if eastern and western meadowlarks are the same species?

The question of whether they can interbreed and produce fertile offspring.

What is the first step in the process of speciation?

The population becomes physically divided.

What happens after a population is physically divided in the speciation process?

Each portion of the divided population begins to follow its own independent evolutionary path.

What accumulates between two populations leading to speciation?

Genetic differences that eventually give rise to reproductive barriers.

What is the relationship between reproductive barriers and gene pools?

Reproductive barriers prevent populations from sharing a gene pool, leading to speciation.

What is an example of behavioral isolation?

Different mating calls in frogs that prevent interbreeding.

What is an example of habitat isolation?

Ladybugs occupying different types of plants.

What is an example of temporal isolation?

Field crickets that mature at different times.

What is mechanical isolation in reproductive barriers?

Mating organs or pollinators are incompatible.

What is gametic isolation?

Gametes cannot unite due to incompatibility.

Define postzygotic reproductive barrier.

Separation of species due to hybrid offspring.

What is hybrid inviability? Provide an example.

Hybrid offspring fail to reach maturity; for example, hybrid eucalyptus seeds are not viable.

What is hybrid infertility? Provide an example.

Hybrid offspring are unable to reproduce; for example, a liger (lion-tiger cross) is infertile.

What is hybrid breakdown?

Second-generation hybrid offspring have reduced fitness; for example, offspring of hybrid mosquitoes have abnormal genitalia.

What do prezygotic reproductive barriers prevent?

They prevent hybrid offspring from occurring between species.

What is temporal isolation?

When species reproduce at different times, preventing mating.

What is habitat isolation?

When species live in different environments and do not meet.

What is behavioral isolation?

When species have unique mating behaviors that prevent interbreeding.

What is allopatric speciation?

A new species forms when a geographical barrier physically separates a population.

Describe the process of allopatric speciation in Galapagos Island tortoises.

Descendants of the first tortoises to arrive colonized the islands, evolving into many subspecies due to unique habitats.

What is sympatric speciation?

A new species arises in the same area as its parent species, often through microenvironmental advantages or hybridization.

How did sympatric speciation occur in Lake Ejagham's cichlid population?

Cichlids in deeper waters evolved smaller bodies compared to shallow-water fish, despite being the same species.

What is an example of mechanical isolation?

Several species of fruit flies in the genus Drosophila have incompatible genitalia.

What happens during gametic isolation?

The egg and sperm of two different species do not fuse or fertilize.

What is an example of hybrid inviability?

The offspring of a donkey and horse (mule) is unable to reproduce.

What is an example of behavioral isolation?

Female fireflies are attracted only to males with a specific flashing pattern unique to their species.

What is an example of temporal isolation?

One species of sea urchin releases gametes in spring while another does so in fall.

What is the significance of genetic divergence in speciation?

It is required for the formation of new species.

What role do geographical barriers play in allopatric speciation?

They physically separate populations, preventing contact and interbreeding.

What is the outcome of hybrid breakdown?

Second-generation hybrids exhibit reduced fitness.

What is the primary factor leading to the divergence of Beetle X variants in the context of Plant X?

The preference of one variant of Beetle X for red flowers, leading to mating and living in those flowers, causing reproductive isolation.

What type of speciation occurs when two populations diverge due to distinct habitat preferences?

Sympatric speciation due to distinct habitat preferences.

What is gradualism in the context of evolution?

Gradualism is the concept that evolution proceeds in small, incremental changes over generations in relatively uniform environments.

What is punctuated equilibrium?

Punctuated equilibrium is a model of evolution that proposes that species experience long periods of stability interrupted by brief bursts of rapid change.

What are some environmental conditions that may lead to rapid bouts of speciation?

Key adaptations in populations, such as flowering plants, that provide advantages in changing environments.

What is extinction?

Extinction is the death of all individuals of a species.

What factors can cause extinction?

Habitat loss, new predators, or new diseases.

What is mass extinction?

Mass extinction is the disappearance of many species over relatively short expanses of time.

What factors may contribute to mass extinction?

Movements of Earth's crust and climate changes.

How should organisms be classified according to biological classification systems?

Organisms should be classified based on their evolutionary relatedness.

What evidence is used to build evolutionary (phylogenetic) trees?

Anatomical features of fossils, existing organisms, behaviors, physiological adaptations, and molecular sequences.

What is a cladogram?

A cladogram is a specific type of evolutionary tree that shows the relationships between organisms.

What do the tips of the branches in an evolutionary tree represent?

The tips represent existing species, while shorter branch tips may represent extinct species.

What does each node (branch point) on an evolutionary tree represent?

Each node represents where two groups arose from a common ancestor.

What does the trunk (root) of an evolutionary tree represent?

The trunk represents the shared ancestors of the organisms depicted in the tree.

In the context of evolutionary trees, what does a longer branch indicate?

A longer branch indicates more evolutionary change over time.

Which node in Xu's dinosaur-bird tree represents the common ancestor for all groups?

Node A represents the common ancestor for all groups.

Which two groups are most closely related in Xu's dinosaur-bird tree?

Troodontids and Dromaeosaurids are the most closely related groups.

What is the significance of the divergence marked by each node in an evolutionary tree?

Each node marks the divergence of an ancestor into two lineages.

What does the term 'phylogenetic' refer to in biology?

Phylogenetic refers to the evolutionary relationships and history among species.

What is the role of reproductive isolation in speciation?

Reproductive isolation prevents interbreeding between diverging populations, leading to speciation.

How does the concept of a key adaptation relate to speciation?

A key adaptation can provide a population with a significant advantage, facilitating rapid speciation in response to environmental changes.