The answer is stabilizing selection.
<span>Sickle-cell anemia is a recessive disorder caused by the presence of two recessive alleles "s", so genotype is "ss". This disorder is characterized by sickle hemoglobin. In an area with malaria, heterozygous individuals "Ss" (with one dominant allele and one recessive allele) have an advantage. These individuals will have both normal and sickle hemoglobin. But pathogen that causes malaria affect only normal hemoglobin, so heterozygous individuals will have half of the hemoglobin resistant to the pathogen and those individuals are resistant to malaria.</span>
Stabilizing selection favors heterozygotes Ss, disruptive selection favors dominant (SS) and recessive (ss) homozygotes, while directional selection favors dominant (SS) or recessive (ss) homozygote. Since in this example, people with genotype Ss (heterozygotes) are in advantage, then this is an example of stabilizing selection.
Answer:
disturbance has destroyed population in a community
Explanation:
The secondary succession occurs after there has been some disturbance that has manged to badly damage or destroy the populations in a community. This basically means that after some catastrophic event that happened to a certain population or populations, other species moved in to colonize the freed space. There are countless examples of secondary succession in nature, and one of the best is when there is a strong volcanic eruption. The volcano manages to destroy the population of plants and animals in its close surroundings, but after the eruption ends, the space starts to be colonized by new plants and animals step by step until they create a new well functioning community.
Answer:
2. 1 Pink : 1 white
3. 1 Red : 1 Pink
4. 1 Red : 2 Pink : 1 White
Explanation:
This question involves a single gene coding for flower colour in snapdragon plants. The alleles of the gene exhibits incomplete dominance i.e. the red allele (R) ia not completely dominant over the white allele (W), hence an intermediate pink phenotype (RW) is formed. Based on this, a red snapdragon will have genotype, CRCR while a white one will have genotype, CWCW. The intermediate pink phenotype will have a genotype, CRCW.
The image attached to this question shows four crosses between different traits.
In the second cross between a pink (CRCW) and white offspring (CWCW), 2pink and 2white offsprings will be possibly produced in the ratio 1:1.
In the third cross between a red (CRCR) and pink (CRCW) snapdragon, 2 red and 2 Pink offsprings will possibly be produced in a ratio 1:1.
In the fourth cross between a pink (CRCW) and pink (CRCW) snapdragon, red, pink and white offsprings will be produced in the ratio 1:2:1.
See attached image for the complete punnet square. Note that, there was a mistake in the Genotype of the last cross i.e. pink has genotype CRCW not CWCW.
