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Chapter 24: Q24-9TYU (page 522)

In sexually reproducing species, each individual inherits DNA from both parent organisms. In a short essay (100鈥�150 words), apply this idea to what occurs when organisms of two species that have homologous chromosomes mate and produce (F1) hybrid offspring. What percentage of the DNA in the F1 hybrids鈥� chromosomes comes from each parent species? As the hybrids mate and produce F2 and later-generation hybrid offspring, describe how recombination and natural selection may affect whether the DNA in hybrid chromosomes is derived from one parent species or the other.

Short Answer

Expert verified

In sexual reproduction, the morphologically different gametes combine and form genetically distinct organisms from parents. Offspring produced from sexual reproduction is unique due to recombination and crossing over.

The sexual reproduction in which two different gametes are combined is called isogamous. The offspring get 50% of the DNA from each parent.

The process of recombination allows a distinct variety of combinations of genes. Therefore, even offspring of the F2 generation produce hybrid offspring. When two genetically different species reproduce sexually, the offspring produced is a mixture of two DNAs. Thus, its unique identity makes them mixed or hybrid.

Natural selection favors genetic variety. The distinct set of chromosomes in every species that reproduce sexually shows successive reproduction. If chromosomes are derived from only one parent, the offspring will look like one of the parents, limiting the genetic divergence.

Step by step solution

01

Sexual reproduction

Genetically divergent offspring are produced from the combination of gametes, and such a process is called sexual reproduction. Sperm and egg are the gametes produced from males and females, respectively.

The evolution of sexual reproduction occurred after the origin of the eukaryotic cell. Most of the eukaryotic organisms鈥� reproductive success is dependent on the sexual mode of reproduction.

02

Recombination in sexual reproduction

The gametes produced through meiotic cell division are distinct and have a set of homologous chromosomes. These are unidentical to parental chromosomes due to the crossing over, which occurs in prophase I of meiosis.

When the gametes fuse during fertilization, the process of recombination results in different combinations of alleles. The random arrangement of genes takes place when recombination occurs.

03

Effect of natural selection on hybrid chromosome derived from one parent

The novel genetic combinations are essential for evolution to happen through natural selection. It facilitates adaptation and accompanies reproductive isolation. The absence of genetic divergence would have zero fitness in individuals. Natural selection favors speciation and always forces for better adaptation.

Therefore, recombination is necessary to achieve reproductive success and increase the survival rate of sexually producing organisms.

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Most popular questions from this chapter

Suppose that females of one population of strawberry poison dart frogs (Dendrobates pumilio) prefer to mate with males that are orange-red in color. In a different population, females prefer males with yellow skin. Explain how such differences could arise and how they could affect the evolution of reproductive isolation in allopatric versus sympatric populations.

Suppose two bird species live in a forest and are not known to interbreed. One species feeds and mates in the treetops and the other on the ground. But in captivity, the birds can interbreed and produce viable, fertile offspring. What type of reproductive barrier most likely keeps these species separate in nature? Explain.

According to the punctuated equilibria model,

(A) given enough time, most existing species will branch gradually into new species.

(B) most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

(C) most evolution occurs in sympatric populations.

(D) speciation is usually due to a single mutation.

State the researchers鈥� hypothesis, and identify the independent and dependent variables in this study. Explain why the researchers used four mating combinations for each pair of populations.

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

(A) The two forms interbreed often in nature, and their offspring survive and reproduce well.

(B) The two forms live in similar habitats and have similar food requirements.

(C) The two forms have many genes in common.

(D) The two forms are very similar in appearance.
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