Bird migrations began with the recession of the glaciers during the ice age. You will notice a great increase in insects in the spring time and early summer.The birds moved North to take advantage of this increase in the food supply that followed the warming in the spring and early summer. Their reproductive organs temporarily developed so they could lay eggs and raise a family. Look at the early flush of Night crawlers in the moist times of the early rains. By mid summer most of the insects have matured, mated and died. Their eggs have hatched and turned to larva and moved underground until next spring. The shortening of the days causes the reproductive functions to decrease and signals the birds that the food will soon become scarce. They move back to the area that makes it the easiest to find food and avoid freezing. which of course is the warmer climates nearer the equator. Not all birds move past the Tropics at approximately 30 degrees. Some like Chickadees may move down from Mi or Mn or Canada only as far south as Indiana. Some migrations may be quite short. For example from the mountains down to the plains. They don't generally reproduce in the warmer winter climes they migrate to. In the spring time they migrate along paths of the retreating glaciers. As the climate warms away from the tropics the birds follow the emerging insects etc to the birds selected breeding grounds.with increased insects and longer days to feed the hatching's. It is necesary to understand why they move to cooler climates in the summer to under stand why they move to eh warmer ones in the fall. As the days shorten the food supply dwindles and the babies have fledged. They move to warmer climates in winter to rest and refuel for the next years migration.
Answer:
Genetic diversity is an advantage of sexual reproduction because it reduces the occurrence of unfavorable genetic traits and a variety of genes would lessen the chance of the extinction of a population due to environmental changes. The variation between a genetically diverse species will guarantee at least some of it survive when presented with different climates or challenges.
The core, or middle, of the Sun is the hottest part. Hot gasses bubble up from the core to the surface of the Sun. When the gasses burn, heat and light are produced.
Answer:
If the two organisms are heterozygous for the dominant trait.
Explanation:
For every trait, a diploid organism receives two forms of gene called ALLELE, from each parent. Allele is the variant form of a gene.
According to Mendel's law of dominance, for a particular trait, an allele is capable of masking the expression of another allele in a gene. The expressed allele is called the DOMINANT allele while the masked allele is called the RECESSIVE allele. Due to this, an organism can express a dominant trait even in a combined or heterozygous state i.e. different alleles.
When the two heterozygous organisms mate or are crossed, they undergo meiosis and their alleles are separated into GAMETES according to Mendel's law of segregation. For example; an organism with genotype (genetic make-up) Aa will produce gametes with A and a alleles.
Note that, a recessive trait can only be expressed in a homozygous state i.e. same allele. Hence, the two heterozygous organisms will produce gametes containing the recessive allele, which will likely combine to produce a recessive phenotype or trait.
The answer is C. The distribution of traits in a population
