History of Evolutionary Thought - Chapter 19

A sharp reduction in population size due to a catastrophic event, leading to a loss of genetic variation and potential for increased harmful alleles. This can occur when the surviving population is not representative of the original population.

A type of natural selection favoring phenotypes at both extremes of the range, leading to two distinct phenotypes within a population.

Natural selection favoring individuals with phenotypes that increase their chances of successfully mating.

Reproductive isolation mechanisms that prevent the formation of a hybrid zygote.

A type of natural selection where the frequency of a phenotype oscillates between generations, driven by the selective pressure of predators or prey favoring the less common phenotype.

The preservation of genetic variation within a population due to the presence of recessive alleles.

The process where traits enhancing survival or reproduction increase in frequency within a population over time, driven by differential reproduction.

A type of natural selection favoring phenotypes at one extreme of the range, leading to a shift in the population towards that extreme.

The stage where immature cells develop into specialized cell types.

The outermost layer of a root, protecting it and facilitating water absorption.

The inner layer of a root, responsible for nutrient storage and support.

The network of tubes that carry water and nutrients throughout the plant, found in both roots and stems.

Specialized pores on the epidermis of leaves that allow for gas exchange, particularly CO2 intake and water vapor release.

The process by which plants continuously grow throughout their lifespan.

Specialized tissues in plants that contain unspecialized cells (like stem cells) that perpetually divide, allowing for continuous growth.

Type of plant growth that involves lengthening of roots and shoots, and the formation of leaves. It occurs at the tips of roots and shoots, and in axillary buds of shoots.

Type of plant growth that involves increasing the girth or width of stems and roots. It occurs in lateral meristems.

Long, thin cells with tapered ends that transport water through pits.

Wider, shorter, thinner-walled cells that are aligned end-to-end, forming long pipes (vessels) for water transport. They have perforation plates that allow water to flow freely.

Long, narrow cells that transport nutrients and lack a nucleus, ribosomes, distinct vacuole, and cytoskeletal elements to allow free passage of nutrients. They are connected by sieve plates with pores.

Cells that help load sugars into sieve tube elements. They are connected to sieve tube elements via plasmodesmata and have all their organelles functional.

The process by which a new species arises when populations are geographically isolated, preventing gene flow. This separation leads to independent evolution and the development of distinct traits.

A region where two geographically isolated populations that have evolved separately come back into contact and potentially interbreed. These zones are a testing ground for the reproductive isolation between species.

In a hybrid zone, this process strengthens reproductive barriers between two species, reducing the chances of hybrids forming. It often involves prezygotic isolation, preventing fertilization.

This outcome in a hybrid zone weakens reproductive barriers between species, leading to a fusion of the two into one. This happens when hybrids are viable and fertile.

This describes a situation where both parent species and hybrid offspring coexist in stable numbers in a hybrid zone. The hybrids may have a limited reproductive ability or be less fit than the parents.

The two-part scientific naming system developed by Linnaeus, where each organism has a genus and species name (e.g., Homo sapiens).

A group of organisms at any rank in the classification hierarchy (domain, kingdom, phylum, class, order, family, genus, species).

A branching diagram used to depict the evolutionary relationships of organisms. It shows the pattern of descent, common ancestors, and evolutionary connections.

The process of a species changing over time, with its descendants having a different appearance due to the accumulation of changes in their traits.

The differences in traits among individuals within a population that are passed down through generations.

Differences in traits among individuals within a population that are not passed down through generations.

The total collection of genes (alleles) in a population, representing the genetic diversity of that population.

The process where allele frequencies in a population change due to random chance events, often more significant in smaller populations.

The transfer of alleles between populations, increasing gene flow.

A situation where a small group separates from a larger population and establishes a new one, often with a different genetic makeup.

The process where individuals with advantageous traits in a specific environment are more likely to reproduce and pass on those traits, leading to an increase in the frequency of those traits in the population over time.

The process where a species evolves into a new species, with the original species remaining.

The process where a species changes over time, resulting in a new species, but the ancestral species is replaced rather than forming a new one.

A point on an evolutionary tree where two lineages diverge, representing a common ancestor.

Two groups of organisms that share an immediate common ancestor not shared by any other group.

A group outside the group being studied on an evolutionary tree, sharing an even more distant common ancestor. It helps determine which traits are ancestral.

Traits shared between species inherited from a common ancestor, regardless of function.

Unrelated species independently evolve similar traits due to adapting to similar environments.

Similar traits that evolve independently in different species, like wings in bats and birds.

A broader term encompassing analogous structures/sequences that evolved independently.

A classification system that focuses primarily on common ancestry to group organisms.

A group of organisms that includes an ancestral species and all of its descendants.

A character present in a group of organisms and their common ancestor, like backbones in vertebrates.

A character present in a group of organisms but not their common ancestor, like feathers in birds.