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Rudiy27
3 years ago
5

Natural selection and genetic drift are two mechanisms of evolution that can lead to speciation. Define both natural selection a

nd genetic drift, describe how both can lead to speciation, and provide both a historic and potentially current example for each. Be sure to address selection pressures
Biology
1 answer:
timofeeve [1]3 years ago
5 0
<h2>Evolution </h2>

Explanation:                  

Genetic drift

  • Genetic drift is change in allele frequencies in a population from generation to generation that occurs due to chance events
  • The genetic drift occurs due to random fluctuation of any allele in a gene pool and is more efficient in small population
  • The founder effect and the bottleneck effect are cases in which a small population is formed from a larger population which means they may experience strong drift for generations
  • In founder effect a genotype from a homogeneous gene pool migrate to a newer habitat and colonize there and form a newer community which leads to the genetic drift to the original population, speciation which occurs in this effect is the peripatric speciation
  • In bottleneck effect the elimination of inferior genotype from a homogeneous gene pool occurs due to the strong selection pressure and changing environmental conditions which leads to genetic drift and a only a few most adapted genotype survives and flourish

Natural Selection

  • Natural selection is a selection pressure which operates in a population and allow the best fitted genotype to survive in changing environmental conditions and eliminate the other genotype which are not fit
  • Genetic drift, mutation and sexual selection are important causes of natural selection
  • Directional natural selection favours the superior genotype and eliminate the inferior and intermediate genotype, in the history of evolution the most common natural selection is directional natural selection
  • Stabilizing natural selection favours the intermediate genotype but eliminates the extreme genotype
  • Bidirectional natural selection favours the extreme genotypes but eliminate the intermediate genotypes

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<u><em>The glucose (sugar or plants food) is then converted back into carbon dioxide which is vital during photosynthesis. This therefore means that when stomata is blocked photosynthesis will stop because the CO₂ level will decline within the leaf, stopping the reactions that are light-independent.</em></u>

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8 0
3 years ago
Read each of the sentences that describe a phase of meiosis. Place each sentence into the correct box.
Allushta [10]

Answer:

prophase 1(Homologous chromosomes pair to form a tetrad.

prophase 1(Crossing-over may occur between the non-sister chromatids).

Metaphase 1 (Homologous chromosomes line up at the center of the cell.)

Anaphase 1 (Homologous pairs separate and move towards opposite ends of the cell)

Telophase 1 (A nuclear membrane forms and cytokinesis follows).

Metaphase 2 ( The haploid number of duplicated chromosomes line up at the metaphase plate.

Anaphase 2 (Sister chromatids separate and become daughter chromosomes that move to the poles)

Meiosis 2: Four haploid daughter cells are formed that are not genetically identical.

Explanation:

Meiosis is a type of cell division that gives rise to gametes ( offsprings). This type of cell division occurs only in the reproductive organs. A diploid cell has two sets of chromosomes: one from the female parent and the other one from the male parent. When the diploid cell undergoes meiosis, the chromosome replicate once and the nucleus and cell duplicate twice giving rise to four haploid gamete cells.

The phases of meiosis occurs in two step divisions. Homologous pairs separate during the first round cell division which occurs in MEIOSIS 1 while the sister chromatids separate in the second nuclear division called MEIOSIS 2.

In each round of division, cells go through four stages: PROPHASE, METAPHASE, ANAPHASE, and TELOPHASE. The specific events that occur in these stages are already listed in the above answer.

Generally, at the start of meiosis, each member of a homologous pair of chromosomes, which are made up of two chromatids, moves to lie side by side. While they are thus paired, genetic material is exchanged between the chromatids. This is known as CROSSING OVER.

When the nucleus divides for the first time, the chromosomes in a given pair( not the chromatids) separate and move to opposite ends of the cell. This results in only half the number of chromosomes going to each daughter cell.

During the second nuclear division, the chromatids separate and move to opposite ends of each daughter cell giving rise to four gamete cells, each with a haploid number of chromosomes.

7 0
3 years ago
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Answer:

It depends entirely on an equation, certain equations are meant to confuse you with numerous answers so taht you have to narrow it down, some only have one or a few. It really depends on the type of problem

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Often the growth cycle of one population has an effect on the cycle of another. As moose populations increase, wolf populations
babymother [125]

Answer:

The correct answer is option D) "K".

Explanation:

In this example the wolf population is described by the equation "ΔN/Δt=rN(K−N)K". Even tough the variables are not defined in the question, we can conclude that the effect of the moose population will be given by a factor that has a positive effect in the wolf's population because "as moose populations increase, wolf populations also increase". The factor "K" fits the description because it gives a positive effect on "ΔN/Δt". "K" is a factor that multiplies "rN" at two different levels, therefore the higher the value of "K", the higher value of "ΔN/Δt" will be.

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