Question

1. Be able to describe/define an animal

2. Be able to describe the early steps in animal development (including cleavage, formation of a blastula, and gastrulation)

3. Know the structures and tissue layers associated with a gastrula (e.g., blastopore, ectoderm, endoderm, etc.)

4. Know why animals are considered to be closely related to choanoflagellates

5. Be able to briefly describe the early radiations of animals (Ediacaran, Cambrian explosion)

6. Know that animal body plans are characterized by symmetry, the number of tissues and their types, and the condition of the body cavity

7. Know the tissue types and some organs/organ systems derived from them (e.g., ectoderm gives rise to the integument and central nervous system)

8. Be able to describe the difference between acoelomate, coelomate, and pseudocoelomate organisms and be able to give an example of an organism for each type of body cavity

9. Be able to describe the differences between protostome and deuterostome development (cleavage, coelom formation, fate of the blastopore)

10. Be able to describe the similarities and differences between animal phylogenies derived from morphological/developmental data versus genetic/molecular data

Answer 1

As per HOMEWORKLIB RULES here answer of first 5 questions are given.

1. Be able to describe/define an animal

Animal is a term used to indicate extremity of an embryo which comprises more active cytoplasm in the early stages of development. Animal nourishes on organic matter. Animals have specialized sense organs, nervous system. They also give rapid response to stimuli.

2. Be able to describe the early steps in animal development (including cleavage, formation of a blastula, and gastrulation)

Early steps in animal development are (including cleavage, formation of a blastula, and gastrulation)

First stage is formation of single-celled zygote which is diploid (2n) in nature. Zygote undergoes mitosis to produce 8 cell stage then it undergoes very rapid meiosis to form blastula stage. The rapid, multiple rounds of cell division are termed cleavage. After cleavage has produced over 100 cells the embryo is known as blastula. In blastula dramatic rearrangement of cells result into development of embryonic tissue layers it is known as gastrulation. Then tissues are produced.

3. Know the structures and tissue layers associated with a gastrula (e.g., blastopore, ectoderm, endoderm, etc.)

Gastrula has 3 germ layers i.e. ectoderm (Outer); mesoderm (Middle); endoderm (Inner). Blastopore is the first opening in development which develop into mouth of animal in protostome development.

4. Know why animals are considered to be closely related to choanoflagellates

There are physical similarities in choanoflagellates and animal cells like feeding cells of sponges known as choanocytes. Sponge choanocytes possess single flagellum and a collar of filaments. In animals also such kind of collars also seen. This similarity shows that unicellular ancestor of animals. In addition to this there is similarity between choanoflagellates and animal at the DNA level. Even some genetic features are similar e.g. 78 pieces of proteins. So due to these resemblances animals are considered to be closely related to choanoflagellates.

5. Be able to briefly describe the early radiations of animals (Ediacaran, Cambrian explosion)

Early radiation of animals include Ediacaran Evolutionary Radiation, Cambrian Explosion, Great Ordovician Biodiversification Interval.

The Ediacaran biota have radiated in Avalon explosion (575 million years ago), after Cryogenian period's extensive glaciation. The Ediacaran radiation is very important with reference to phylogenetic, evolutionary and ecological rise of animals. All present era animals first appeared in the fossil record in Cambrian than Ediacaran radiation.

The Cambrian period (nearly 542–488 million years ago), considered as the most rapid evolution of new animal phyla and animal diversity. Most of the animal phyla in existence in present era have evolved in Cambrian period it is known as Cambrian explosion. Earlier to this Cambrian explosion, maximum organisms were simple but then evolved.