Animal Classification, Development, and Evolution: Key Concepts and Phylogenetics

What are the five primary criteria used to classify animals?

Anatomy, morphology, evolutionary history, embryonic development, and genetic makeup.

What are the defining characteristics of the animal kingdom?

Obligate heterotrophs, complex tissue structures with specialized cells, motility, diplontic life cycles, and predetermined body plans.

Why do animals possess specialized structures like sensory organs and complex neurological networks?

These structures evolved to help animals seek out food and avoid becoming food for others.

What is a major structural difference between animal cells and plant cells?

Animal cells lack cell walls.

Define the term Eumetazoa.

Eumetazoa refers to 'true animals' that possess specialized tissues.

Which animal group is characterized by having no specialized tissues?

Parazoa or Porifera (sponges).

What is the typical ploidy of animal somatic cells and gametes?

Somatic cells are diploid, while gametes are haploid.

What is a notable exception to the diploid rule in Hymenoptera?

Males arise from unfertilized eggs and are therefore haploid organisms.

What is parthenogenesis as seen in the New Mexico Whiptail lizard?

A form of asexual reproduction where eggs develop into embryos without fertilization.

What occurs during the cleavage stage of embryonic development?

Mitotic cell division occurs without cell growth, resulting in the production of blastomeres.

What is the primary function of gastrulation?

To produce the digestive tube and the germ layers.

What are the three germ layers and their general functions?

Ectoderm (exterior surface), endoderm (lining of the digestive tract), and mesoderm (structures between the ectoderm and endoderm).

What is the difference between incomplete and complete metamorphosis?

In incomplete metamorphosis, young look like small adults; in complete metamorphosis, young differ from adults in both form and behavior.

What is the function of Hox genes?

They serve as master controlling genes that determine the general body plan, including body segments, limb placement, and head/tail directionality.

Why are phylogenetic trees considered hypotheses?

Because our understanding of evolutionary relationships is constantly changing as new molecular information becomes available.

What is the difference between protostomes and deuterostomes?

In protostomes, the mouth forms before the anus; in deuterostomes, the anus forms before the mouth.

What is the significance of the Ediacaran biota?

They represent early animal life, thought to have evolved from protists, with no living representatives today.

What was the Cambrian Explosion?

A period approximately 542-488 million years ago characterized by the most rapid evolution of new phyla and diversity in Earth's history.

What was the trilobite's significance in the Cambrian period?

It was one of the dominant species and one of the first animals to display a sense of sight.

List three environmental factors that may have contributed to the Cambrian Explosion.

Rise in atmospheric oxygen, increased calcium in oceans, and the availability of shallow lagoons on continental shelves.

How did the evolution of Hox genes contribute to animal diversification?

It increased morphological variability by allowing for more complex body plans.

What major biological event occurred during the Ordovician period?

An explosion of terrestrial plant life, which led to the expansion of animal species.

How do mass extinction events influence evolution?

They lead to the evolution of new species through the mechanism of genetic drift.