Animal Diversity and the Evolution of Body Plans

Flashcards reviewing key concepts from a lecture on animal diversity and the evolution of body plans.

What is heterotrophy in animals?

Obtaining energy and organic molecules by ingesting other organisms.

What is a key characteristic of animal cells related to cell walls?

They lack rigid cell walls and are usually flexible.

How diverse are animal habitats?

Grouped into 35 to 40 phyla, most occur only in the sea, but many occur in fresh water and on land.

How do most animals reproduce?

Sexually.

What are the five key innovations in animal evolution?

Symmetry, Tissues, Body cavity, Various patterns of embryonic development, Segmentation

What type of symmetry do sponges have?

Lack any definite symmetry

What are the two main types of symmetry in animals?

Radial and Bilateral

What are the characteristics of radial symmetry?

Body parts are arranged around a central axis, can be divided into two equal halves by any plane through the center

What are the characteristics of bilateral symmetry?

Body has right and left halves that are mirror images; only the sagittal plane bisects the animal into two equal halves

What are two advantages of bilateral symmetry over radial symmetry?

Cephalization (evolution of a definite brain area) and Directional movement

What is a key difference between sponges and other animals regarding tissues?

Sponges do not have defined tissues and organs; other animals have distinct and well-defined tissues.

What are the three germ layers produced by most animal embryos (triploblastic)?

Ectoderm, Mesoderm, Endoderm

Which germ layer forms the body coverings and nervous system?

Ectoderm

Which germ layer forms the skeleton and muscles?

Mesoderm

Which germ layer forms the digestive organs and intestines?

Endoderm

What germ layers do cnidarians have?

Endoderm and ectoderm. They are diploblastic.

What are the three basic kinds of body plans?

Acoelomates, Pseudocoelomates, and Coelomates

What is a coelom?

Body cavity entirely within the mesoderm tissue that is formed during development.

What is the difference between open and closed circulatory systems?

Open: blood passes from vessels into sinuses. Closed: blood moves continuously through vessels separate from body fluids.

What is a blastula?

A hollow ball of cells formed during mitotic cell divisions (cleavage) of the egg

What is a blastopore?

The opening to the outside formed when the blastula indents

What is the difference between protostomes and deuterostomes in terms of blastopore development?

Protostomes develop the mouth first, from or near the blastopore. Deuterostomes develop the anus first from the blastopore.

What is the cleavage pattern in protostomes?

Spiral cleavage (new cells form to the right or left of previous cells)

What is the cleavage pattern in deuterostomes?

Radial cleavage (new cells form on top of previous cells)

What is determinate development?

Cell fate is determined early (characteristic of protostomes).

What is indeterminate development?

Cell fate is not determined until after several divisions (characteristic of deuterostomes).

How does coelom formation differ between protostomes and deuterostomes?

Protostomes: cells move apart to form coelom. Deuterostomes: groups of cells pouch off to form coelom.

What are two advantages of segmentation?

Allows redundant organ systems and more efficient, flexible movement.

How are animals divided into main branches?

Sponges (Parazoa) and Eumetazoa (all animals other than sponges).

What are the major clades within Bilateria?

Deuterostomes and Protostomes

What is the major characteristic of Ecdysozoa?

Animals that molt. ex:Jelly fish, Cnidarians

What are the two main branches of Kingdom Animalia (Metazoa)?

Parazoa and Eumetazoa

What is the primary characteristic of Parazoa?

Animals lacking tissues (and therefore organs) and a definite symmetry. Ex:Sponges.

Which phylum belongs to the Parazoa?

Phylum Porifera (sponges).

What is the habitat of most sponges?

Marine. However, 150 species live in freshwater.

What is the adult form of sponges?

Sessile (attached)

What are the three functional layers in the vase-shaped body of a sponge?

Outer epithelium, mesohyl, and lining of the internal cavity

What are spicules?

Needles of calcium carbonate found in the mesohyl of sponges.

What are choanocytes?

Collar cells that line the internal cavity of sponges; they are flagellated and engulf food.

How do sponges reproduce asexually?

Fragmentation.

How do sponges reproduce sexually?

Choanocytes transform into sperm, sperm are captured and passed to egg cell in mesohyl, development may occur within mother or in open water.

What are the characteristics of Eumetazoa?

Animals with true tissues, definite shape and symmetry, and possibly organs and organ systems.

What is the inner endoderm in eumetazoans?

Forms the gastrodermis.

What is the outer ectoderm in eumetazoans?

Forms the epidermis and nervous system.

What are colloblasts?

Adhesive cells found on the tentacles of ctenophores used to capture prey.

What is a unique feature of cnidarians?

They capture prey with nematocysts.

What are the two basic body forms of cnidarians?

Polyps and Medusa

Which phylum has a body plan with a single opening leading to a gastrovascular cavity?

Cnidaria

What is gonochorism?

Individual is either male or female. This occurs in Cnidarians

What is planula?

Zygote develops into planktonic planula. This occurs in Cnidarians

What is the function of nematocysts?

Capture prey; secreted within nematocyte, some carry venom.

What is a key characteristic of Anthozoa?

Solitary and colonial polyps.

What are zooxanthellae?

Symbiotic dinoflagellates which photosynthesize and provide nutrients to reef coral.

What is the nervous system like in Acoel flatworms?

It has a primitive system, and lacks a digestive cavity.