Animal Characteristics

Flashcards summarizing key concepts related to the characteristics, reproduction, and development of animals.

Animals are __, eukaryotic heterotrophs that have evolved to live in many different habitats.

multicellular

The __ is a fluid-filled ball of cells formed during early embryonic development.

blastula

Internal fertilization occurs when sperm and egg meet __ an animal’s body.

inside

The outer layer of the gastrula develops into the __, which becomes the nervous system and skin.

ectoderm

Most animals reproduce __, while some are hermaphrodites, producing both sperm and eggs.

sexually

The __ is the fertilized egg formed when sperm penetrates the egg.

zygote

Many invertebrates are covered by __, which are hard or tough outer coverings.

exoskeletons

The stage after the blastula where the cells form a two-cell-layer sac with an opening at one end is called __.

gastrula

Between 95-99 percent of animals are __, animals without backbones.

invertebrates

The inner layer of the gastrula develops into the __, which forms the digestive organs.

endoderm