What characteristic is most unique to animals?

Question

A) Formation of specialized layers during development

B) Sexual reproduction

C) Multicellularity

D) Heterotrophic nutrition

My Guess is A because both plants and animals can s e x u a l l y reproduce (some plants not all), are multicellular and can have heterotrophic nutrition (Some plants not all).

Answer 1

Well done! You gave some accurate explanations for why the answer would be A. Let's add a bit more detail to what you already said and enhance our understanding of why A is the answer.

The question is asking what characteristic is MOST unique to animals, so it is important to rule out characteristics that many organisms would have in common with animals.

A) Formation of specialized layers during development

Animals are made of many systems that the body has to account for during development. Animals develop what are called germ layers and these layers will eventually turn into the organism's body systems. This happens during the gastrulation stage of embryological development.

Some organisms within the animal kingdom do not have all germ layers. The three germ layers that animals can develop are endoderm (from which the digestive system would develop), mesoderm (from which muscles and bones would develop), and ectoderm (from which the skin would develop).

B) Sexual reproduction

This is simply the result of a male and female from any species creating offspring. This is seen in many types of organisms.

C) Multicellularity

Many types of organisms are multicellular: plants, fungi, and protists (like Kelp). So this would not be one of the MOST unique aspects of animals.

D) Heterotrophic nutrition

Again, this is a characteristic found in multiple types of organisms, which does not make this the most unique to animals. If an organism needs to consume to obtain energy, then the organism is heterotrophic. Fungi, protists, and bacteria can fit this description, as well.

Answer 2

D) Heterotrophic nutrition is the characteristic that is most unique to animals. Heterotrophic nutrition refers to the ability of animals to obtain energy by consuming other organisms or organic matter, as opposed to autotrophic organisms that can produce their own energy through photosynthesis. While other characteristics listed - formation of specialized layers during development, sexual reproduction, and multicellularity - are also important features of animals, they are not unique to animals and can be found in other living organisms as well.