Speciation: Allopatric vs Sympatric

Allopatric speciation occurs through geographic isolation, while sympatric speciation happens without geographic separation.

Peripheral isolation creates small, isolated populations that experience different selection pressures, leading to genetic drift and incipient differentiation.

Genetic drift causes random changes in the genetic structure of isolated populations, contributing to the divergence necessary for allopatric speciation.

<p>Polyploidy allows plants to have multiple sets of chromosomes, leading to reproductive isolation and the ability to speciate without geographic separation.</p> Signup and view all the answers

<p>Darwin's Finches exemplify allopatric speciation, with different species evolving distinct bill sizes and feeding habits due to geographic isolation.</p> Signup and view all the answers

<p>Allopatric speciation occurs when populations are geographically separated by barriers, leading to the development of distinct species.</p> Signup and view all the answers

<p>Sympatric speciation is less common because it occurs within the same geographic area, making it harder for species to diverge.</p> Signup and view all the answers

<p>East African Cichlids illustrate sympatric speciation by diversifying into multiple species due to ecological niche differentiation and selective pressures within Lake Victoria.</p> Signup and view all the answers

<p>Sexual selection maintains sympatric speciation by favoring non-random mating, where females choose mates based on preferred traits, thus preventing interbreeding.</p> Signup and view all the answers

<p>Factors leading to sympatric speciation in cichlids include habitat separation and dietary differences, which promote ecological specialization.</p> Signup and view all the answers

<p>Reproductive barriers prevent gene flow between populations, leading to the formation of new species.</p> Signup and view all the answers

<p>Habitat isolation occurs when two species live in different environments and do not meet to mate; for example, one species living in trees and another on the ground.</p> Signup and view all the answers

<p>Behavioral isolation arises when species have different mating rituals or behaviors, causing them to not recognize each other as potential mates.</p> Signup and view all the answers

<p>Gametic isolation prevents sperm from fertilizing eggs of different species, often due to incompatibility of gametes.</p> Signup and view all the answers

<p>Reduced hybrid viability refers to the lower likelihood of survival for hybrids produced by mating between two different species.</p> Signup and view all the answers

<p>Non-random mating can lead to changes in allele frequencies within a population, promoting genetic differentiation.</p> Signup and view all the answers

<p>Selection, or natural selection, is an agent of evolutionary change that results in favorable traits becoming more common in a population over time.</p> Signup and view all the answers

<p>Speciation is the process through which new species arise from existing species, contributing to biological diversity by allowing for the differentiation of populations over time.</p> Signup and view all the answers

<p>Anagenesis involves the accumulation of heritable changes leading to the transformation of a single species over time, while cladogenesis results in the branching off of new species from a parent species.</p> Signup and view all the answers

<p>The BSC is limited because it does not apply to asexually reproducing species, and it overlooks species that may not hybridize in nature despite being capable of interbreeding under specific conditions.</p> Signup and view all the answers

<p>The BSC relies on the criteria of actual or potential interbreeding among populations, focusing on reproductive isolation from other populations.</p> Signup and view all the answers

<p>Geographic barriers may lead to populations being considered the same species under the BSC if they are presumed capable of interbreeding, regardless of physical separation.</p> Signup and view all the answers

<p>Yes, hybridization in controlled environments may suggest that certain plant species are evolutionarily distinct even if they do not hybridize in nature, complicating the species definition.</p> Signup and view all the answers

<p>The morphological species concept classifies species based on physical similarities that distinguish them from other groups, focusing on observable traits.</p> Signup and view all the answers

<p>Considering species with non-genetic reproductive barriers forces reevaluation of the BSC and challenges the notion of species as strictly defined by genetic interfertility.</p> Signup and view all the answers

<p>The kdr allele carries a recessive trait conferring resistance to DDT, which, after 2006, was found in A.coluzzii due to hybridization.</p> Signup and view all the answers

<p>Punctuated equilibrium posits that species experience long periods of stasis interrupted by brief, significant evolutionary changes, contrasting Darwin's idea of gradual change over time.</p> Signup and view all the answers

<p>G.G. Simpson highlighted the importance of both tempo and mode in evolution, paving the way for further exploration by Gould and Eldridge into the pace of evolutionary changes.</p> Signup and view all the answers

<p>Neutral selection suggests that some changes occur without affecting an organism's fitness, contradicting the idea that all evolutionary changes must be beneficial for survival.</p> Signup and view all the answers

<p>Reproductive isolating barriers prevent different species from interbreeding, which is crucial in maintaining species integrity and facilitating speciation.</p> Signup and view all the answers

<p>Allopatric speciation often leads to punctuated equilibrium, where physical separation of populations results in rapid evolutionary changes during periods of environmental stress.</p> Signup and view all the answers

<p>Hybridization introduced the resistant kdr allele into A.coluzzii, which may accelerate the spread of DDT resistance in mosquito populations.</p> Signup and view all the answers

<p>Punctuated equilibrium is supported by the rarity of transitional fossils, suggesting that evolution typically occurs in rapid bursts rather than gradual changes.</p> Signup and view all the answers

<p>Polyploidy is the condition of having multiple complete sets of chromosomes greater than 2n. It is more common in plants because they can undergo self-fertilization, allowing easier propagation of new polyploid generations.</p> Signup and view all the answers

<p>Viable polyploids tend to be vigorous and, in the case of animals, are often larger in size. This increased vigor can contribute to their success in various environments.</p> Signup and view all the answers

<p>Sympatric speciation occurs when a subset of a population becomes reproductively isolated without geographic separation. This requires the emergence of barriers to gene flow that separate gene pools.</p> Signup and view all the answers

<p>A hybrid zone is a region where different species co-occur and interbreed. It allows for gene flow between species but presents challenges for maintaining reproductive isolation.</p> Signup and view all the answers

<p>Reinforcement occurs when strong reproductive barriers develop in areas where species overlap, leading to increased mate choice by females for males of their own species. This enhances reproductive isolation.</p> Signup and view all the answers

<p>Fusion occurs when two incipient species merge back together due to significant gene flow, resulting in a failure of speciation. This can happen when environmental factors obscure distinguishing traits.</p> Signup and view all the answers

<p>Stability in hybrid zones refers to a situation where hybrids are produced but have low viability, ensuring that the parent species remain distinct despite ongoing hybridization. Gene flow is restricted.</p> Signup and view all the answers

<p>The potential outcomes in a hybrid zone include reinforcement of species barriers, fusion of species, or stability of the hybrid zone with separate species remaining distinct. The balance of gene flow determines these outcomes.</p> Signup and view all the answers

<p>Polyploids have more than two sets of chromosomes, making it impossible for them to pair their chromosomes correctly with diploid individuals during meiosis. This leads to immediate reproductive isolation.</p> Signup and view all the answers

<p>Self-fertilization allows plants to reproduce successfully with their own gametes, thus enabling polyploids to proliferate without needing a mate, which facilitates the establishment of a stable population.</p> Signup and view all the answers

<p>Female mate choice is crucial in reinforcement as it promotes mating with males of the same species, increasing reproductive barriers and promoting speciation. This can lead to distinct mating preferences in overlapping regions.</p> Signup and view all the answers

<p>Gene flow in hybrid zones can lead to the mixing of genetic material between species, affecting the evolutionary dynamics of both species and potentially leading to reinforcement, fusion, or stability.</p> Signup and view all the answers

<p>Environmental changes, such as pollution that alters visibility, can reduce mate selection pressures, causing two distinct species to interbreed indiscriminately, leading to fusion.</p> Signup and view all the answers

<p>Reinforcement illustrates sympatric speciation by showing that stronger reproductive barriers develop where species overlap, leading to selective mating and promoting divergence.</p> Signup and view all the answers

<p>Hybridization can complicate speciation by introducing gene flow between species that may otherwise be diverging, possibly leading to fusion or stability rather than distinct speciation.</p> Signup and view all the answers