Answer:
Mechanical incompatibility.
Explanation:
Mechanical incompatibility: occurs when species cannot mate because their reproductive structures are incompatible – In animals with internal fertilization, male and female sexual organs may not fit together – For example, snails of species whose shells have left-handed spirals may be unable to copulate successfully.
Mechanical incompatibility of male and female genitalia is common in animals with internal fertilization. However, our knowledge regarding the precise mechanisms is limited.
Spring tide is the high tide and neap tide is the low tide
Answer:
d. Estrogen will bind to a receptor protein that enters the nucleus and activates specific genes.
Explanation:
Estrogens are small lipophilic molecules synthesized from cholesterol. This steroid hormone (estrogen) is able to directly enter into the cell nucleus to bind with their corresponding receptors. Subsequently, estrogen-receptor binding stimulates these receptors to form dimeric structures that bind to DNA and thus activate gene expression. Estrogen receptors interact with DNA and activate gene expression through zinc finger domains composed of four (4) cysteine residues surrounding a zinc atom.
