The first trimester is the most vulnerable.
Answer: All birds are warmblooded, or endothermic, animals. Birds are vertebrates because
they have backbones. All birds have a four-chambered heart, a
characteristic they share with mammals. All birds lay hardshelled eggs. Birds have only two legs. Their forelimbs have
become modified into wings for flying. All modern birds evolved
from ancestors that could fly.
Explanation:
Answer:
Heterozygous dominant (Bb) and homozygous recessive (bb)
Explanation:
This cross involves the gene that codes for color blindness in whales. The allele for no color blindness/normal vision (B) is dominant over the allele for color blindness (b). This means that B will mask the phenotypic expression of b in a heterozygous state (Bb).
According to the question, one of the parents is color blind meaning it possesses the homozygous recessive genotype (bb) while the other parent (pearl) has a normal vision which can either be homozygous dominant or heterozygous dominant since the normal vision allele (B) is dominant.
However, since one of the two offsprings (sons) is also color blind, this implies that the parent with normal vision is heterozygous i.e. contains both dominant and recessive alleles, for the trait. What happens is that, when a bb and Bb parent are crossed, they produce gametes with either a recessive or dominant allele.
The Bb produces gametes with B and b alleles while the bb produces gametes with b and b alleles. When this are crossed using a punnet square, four possible offsprings will be produced with two distinct genotypes: Bb and bb. Hence, this means that there is a 1/2 chance of producing an offspring with the recessive trait from this cross as the case is in the whales.
The body can defend itself from pathogens using white blood cells, the respiratory system, and digestive system. White blood cells fight against the pathogens by ingesting them. Certain white blood cells called lymphocytes produce antibodies that destroy pathogens by finding antigens, the foreign chemicals released by the pathogen. The respiratory system defends the body from pathogens each time you sneeze or cough. Cilia and mucus also protect the body by trapping dirt and other particles. The digestive system destroys pathogens with saliva, mucus, enzymes, and stomach acid.
