Chapter 30 Intro to Animals

What defines animals under the Opisthokonta lineage?

Animals share a common ancestor with fungi and choanoflagellates, are multicellular eukaryotes, and are heterotrophic.

What key event marked the rapid diversification of animals around 550 million years ago?

The Cambrian explosion.

What are the two primary types of body symmetry in animals?

Radial symmetry and bilateral symmetry.

What is the function of choanocytes in sponges?

They help trap bacteria and organic debris for feeding.

Define diploblastic animals.

Animals that have two embryonic germ layers: ectoderm and endoderm.

What is cephalization?

The concentration of sensory organs and the mouth in the head region of an animal.

What distinguishes protostomes from deuterostomes in terms of embryonic development?

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

What are three types of skeletal systems found in animals?

Hydrostatic, endoskeletons, and exoskeletons.

What is the difference between direct and indirect development in animal life cycles?

Direct development produces young that look like smaller adults, while indirect development involves radically different larvae.

Give an example of a feature unique to the feeding process of cnidarians.

They possess specialized cells called cnidocytes that eject barbed structures to capture prey.

What is metamorphosis in the context of animal life cycles?

A drastic change in form from one developmental stage to another.

What term describes animals that have an internal body cavity completely lined with mesoderm?

Coelomates.

What is bilateral symmetry?

A body plan with a single plane of symmetry, usually resulting in two mirrored halves.

Describe the feeding habits of detritivores.

Detritivores feed on dead organic matter.

What role do limbs play in animal diversity?

Limbs contribute to diverse modes of movement and adaptations in various animal species.

What is the acoelomates classification in relation to body cavities?

Acoelomates lack an enclosed body cavity (coelom) and have solid bodies.

What type of reproduction do viviparous animals exhibit?

Viviparous animals nourish embryos internally and give birth to live young.

How do protostomes and deuterostomes differ in their evolutionary significance?

Protostomes include most animal species while deuterostomes encompass larger animals and predators.

What adaptive significance does metamorphosis hold for larvae and adults of the same species?

It reduces competition for food between larvae and adults as they exploit different resources.

What are the two stages of cnidarians' life cycles?

The sessile polyp form that reproduces asexually and the free-floating medusa that reproduces sexually.

What is the central nervous system's relationship with cephalization?

Cephalization contributes to the evolution of the central nervous system by clustering sensory organs in the head.

Define pseudocoelomates.

Pseudocoelomates have an enclosed body cavity that is partially lined with mesoderm tissue.

What evolutionary links are suggested between the nervous system and bilateral symmetry?

The evolution of the nervous system and head are tightly linked to bilateral symmetry, contributing to bilaterian radiation.

What indicates the closest living relatives to sponges?

Choanoflagellates are considered the closest living relatives to sponges.