external fertilization
: fish (exception of some sharks), amphibians
metamorphosis
: insects, amphibians, echinoderms and starfish
spinal cord
: all vertebrates
scales
: reptiles, fish, mammals, birds
ectothermic
: fish, amphibians, reptiles
amniotic eggs
: birds, mammals, reptiles
gills in adults
: fish
lungs in adults: mammals, birds, reptiles, amphibians
Explanation:
External fertilization is fertilization i.e. fusion of egg and sperm outside the body of the female. This usually occurs in fish and amphibians.
Metamorphosis refers to the developmental stages of insects, amphibians and echinoderms. It involves continuous change in shape or form during the life cycle.
A spinal cord protected by the vertebral column is a feature of all vertebrates.
Ectothermic animals are cold blooded i.e. they cannot regulate their body temperatures. Their body temperature changes with external changes.
Amniotic eggs refer to eggs with a yolk or amniotic sac around the embryo. The amniotic sac protects the embryo. In the case of birds, it provides nutrients.
