Most fish exchange gases using gills<span> on either side of the </span>pharynx<span> (throat). Gills are tissues which consist of threadlike protein structures called </span>filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia.<span>Each filament contains a </span>capillary<span> network that provides a large </span>surface area<span> for exchanging </span>oxygen<span> and </span>carbon dioxide<span>. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing </span>countercurrent exchange<span>. The gills push the oxygen-poor water out through openings in the sides of the pharynx. Some fish, like </span>sharks<span> and </span>lampreys<span>, possess multiple gill openings.</span>
Marine mammals , with few exception are viviparous.
Explanation:
- Mammals are those animals which are characterized by the presence of mammary gland and body hair.
- They feed milk to their young ones.
- The vertebrates are classified as viviparous, oviparous and ovoviviparous depending on the way their young ones develop and are nourished during their embryonic and foetal development.
- Viviparous animals are those which directly give birth to their young ones and have a distinct gestation period during which their babues develop inside their womb. These are placental mammals.
- Oviparous animals are those which lay egg and the embryo develops outside mothers body.
- Ovoviviparous animals are those who do not lay their eggs but their eggs hatch inside their body .These are aplacental animals.
- Most mammals are viviparous.
Answer:
I'm not 100% sure but I'm positive the answer was or is Methane, correct me if I'm wrong!
