Chapter 32 intro to animal diversity

General Characteristics of Animals

1. Animals have eukaryotic cells with no cell walls and are multicellular.

2. Animals are heterotrophs- obtain their energy from other organisms. Most ingest (eat) food then using enzymes digest it within their bodies

3. Animals reproduce both sexually with the fusion of gametes (eggs and sperm) and asexually not involving sex cells. The diploid stage usually dominates the life cycle.

4. Sexually reproducing animals have a life cycle that includes a blastula stage in which the cell division of the zygote produces a hollow ball of cells. Following this stage, a gastrula stage forms where the cells become arranged as “primary tissue” or germ layers that give rise to the adult’s tissues and organs.

blastula stage

stage in animal sexual reproduction where the cell division of the zygote produces a hollow ball of cells

gastrula stage

Following the blastula stage, forms where the cells become arranged as “primary tissue” or germ layers that give rise to the adult’s tissues and organs.

Animal Body Plans: Symmetry

A. Body Symmetry

1. Radial Symmetry- a body plan having parts arranged regularly around a central axis, like spokes on a bicycle wheel.

2. Bilateral Symmetry- a body plan in which left and right halves are mirror images of each other. Bilateral animals have an anterior end (toward the front or head) and an opposite, posterior end (toward the rear or tail). They also have a dorsal surface (back) and an opposite, ventral surface (belly).

Animal Body Plans: Tissues

1. Sponges and a few other animals lack tissues, groups of similar cells that act as a functional unit.

2. During gastrulation cells become arranged in primary tissues or germ layers.

3. The ectoderm gives rise to the outer layer of the animal and in some phyla, the central nervous system.

4. The endoderm the innermost germ layer gives rise to the lining of digestive tract (or cavity) and to the lining of organs such as the liver and lungs in vertebrates.

5. Cnidarians and a few other groups of animals have only these two germ layers and a re called diploblastic.

6. All other animals have a third germ layer called the mesoderm that forms the muscles and most other organs between the digestive tract and the outer covering of the animal. These animals are called triploblastic, having three germ layers, and are more complex in structure.

ectoderm

gives rise to the outer layer of the animal and in some phyla, the central nervous system.

endoderm

the innermost germ layer gives rise to the lining of digestive tract (or cavity) and to the lining of organs such as the liver and lungs in vertebrates

diploblastic

two germ layers

IE: Cnidarians

mesoderm

forms the muscles and most other organs between the digestive tract and the outer covering of the animal

triploblastic

having three germ layers, and are more complex in structure.

Animal Body Plans: Segmentation

is a subdivision along the length of the animal body into a series of repeated parts called segments.

Animal Body Plans: Cephalization

1. is the concentration of sensory structures and nerve cells in the head.

2. This is advantageous for a bilateral, forward moving animal, because their anterior end is the first to encounter food and other stimuli.

Animal Body Plans: Type of Gut

The gut is a body region where food is digested and then absorbed.

1. Saclike (Blind sac) Gut- has only one opening (a mouth) for taking in food and expelling residues.

2. Tubelike Gut- "complete digestive tract" has two openings, a mouth and anus. They are more efficient because they have different regions with specialized functions (preparing, storing and digesting food).

Animal Body Plans: Body Cavities.

A body cavity is a fluid-filled space surrounding the gut.

1. Acoelomate

2. Pseudocoelomate

3. Coelomate

Acoelomate

a type of animal that has no cavity surrounding the gut.

Pseudocoelomate

a type of animal that has a body cavity that is not lined with a peritoneum.

Coelomate (Eucoelomate)

an animal that has a peritoneum lining surrounding the body cavity, called a coelom. The coelom protects and cushions the organs and the peritoneum holds the organs in place.

coelom

Body cavity surrounded by a peritoneum lining, it protects and cushions the organs.

peritoneum

Holds organs in place, surrounds coelom

Protostome and Deuterostome Development

Many animals can be described as having one of two developmental modes: protostome or deuterostome development.

Protostomes

1. In animals with protostome development, early cell division occurs as spiral cleavage,

2. As seen in the eight-cell stage of the embryo, smaller cells are centered over the grooves between larger, underlying cells.

3. Protostomes also have determinate cleavage

4. The first indentation in the early embryo develops into the mouth (proto- first, stoma- mouth).

5. Protostomes include mollusks, annelids, and arthropods.

spiral cleavage

in which the planes of cell division are diagonal to the vertical axis of the embryo.

As seen in the eight-cell stage of the embryo, smaller cells are centered over the grooves between larger, underlying cells.

determinate cleavage

1. In which the developmental fate of every embryonic cell is determined early.

2. For example: a cell isolated at the four-cell stage cannot develop into a whole organism; the embryo will lack many parts.

3. The first indentation in the early embryo develops into the mouth (proto- first, stoma- mouth).

Deuterostomes

1. In animals with deuterostome development have radial cleavage in which the cleavage planes are either parallel or perpendicular to the vertical axis.

2. In the eight-cell stage, tiers of cells are aligned, one directly above the other.

3. Deuterostomes also have indeterminate cleavage, meaning that each cell produced by early cleavage retains the capacity to develop into a complete embryo.

4. The first indentation in the early embryo develops into the anus and the second indentation develops into the mouth (deuteros- second, stoma- mouth). Deuterostomes include echinoderms and chordates.