Introduction to Animals

• Over a million different types have been identified!

• Animals likely evolved from protozoans.

Kingdom Protista

Section 11. blastula (596)2. ectoderm (596)3. endoderm (596)4. mesoderm (596)5. body plan (598)6. asymmetrical (598)7. radial symmetry (598)8. bilateral symmetry (598)9. cephalization (599)10.coelom (600)11.acoelomate (600)12.pseudocoelomate (600)13.coelomate (600)14.phylogenetic tree (602)

Characteristics of Animals

All animals share these general features: 1. heterotrophy,2. mobility, 3. multicellularity, 4. sexual reproduction, 5. diploidy,6. the absence of a cell wall, 7. cells organized as tissues, and8. blastula formation.

heterotrophy,

Can’t make their own food… must eat things.

mobility,

• Animals can swim, crawl, walk, run, and even fly.

• Some only move in the larval stage… the sponge

multicellularity,

• Made up of more then one cell!

• Although animals come in a wide range of sizes, the cell sizes are all very similar!

sexual reproduction• Almost all animals reproduce sexually by

producing gametes.

• Unlike the egg cells, the sperm cells of animals have a flagella and are highly mobile.

diploidy,

adults have two copies of each chromosome, one inherited from their father and one from their mother.

the absence of a cell wall,

Among the cells of multicellular organisms, only animal cells lack rigid cell walls. The absence of a cell wall has allowed animals mobility that other multicellular organisms do not have.

blastula formation

In all animals except sponges, the zygote (fertilized egg cell) undergoes cell divisions that form a hollow ball of cells called a blastula.

cells organized as tissuesCells within the blastula eventually develop into three distinct layers of cells endoderm, ectoderm, and mesoderm . These layers are called the primary tissue layers because they give rise to all of the tissues and organs of the adult body.

tissues

tissues are groups of cells with a common structure that work together to perform a specific function.

Body Symmetry

All animals have their own particular body plan, a term used to describe an animal’s shape, symmetry, and internal organization.

3 body symmetry

Asymmetry.

Animals that grow in an irregular pattern, such as a sponge, show asymmetry.

radial symmetry

Animals with radial symmetry have body parts arranged

around a central axis.

bilateral symmetry

Animals with bilateral symmetry have

a distinct right and left half, and most display cephalization.

body plansAnimals have one of three basic body plans:

acoelomate, pseudocoelomate, and coelomate.

coelom

a body cavity, coelom or (SEE luhm), a fluid-filled space found between the body wall and the digestive tract (gut).

This space is lined with cells that come from mesoderm.

• Coelomates are either protostomes or deuterostomes.

• Protostomes (first mouth) are coelomates whose embryonic development shows a blastopore associated with a mouth.

• Deuterostomes (second mouth) are coelomates whose embryonic development shows a blastopore associated with an anus, with a second opening forming the mouth (hence "second mouth").

acoelomateAnimals with no body cavity

are called acoelomate (ay SEEL oh mayts).

The space between an acoelomate’s body wall and gut is completely filled with tissues

pseudocoelomatehave a body cavity located

between the mesoderm and endoderm. Their body cavity is called a pseudocoelom (false coelom)

Body plans

Segmentation

Segmentation in body structure underlies the organization of all advanced animals.

• Some animals have their bodies divided into segments. This allows them to specialize certain segments, such as for antennae, eyes, claws, etc. Humans, insects, and earthworms are examples of segmented animals.

animal phylaThere are about

35 animal phyla, which contain an extraordinary range of body forms and body systems.

.

phylogenetic tree

To visually represent the relationships among various groups of animals, scientists often use a type of branching diagram called a phylogenetic tree.

It shows how animals are related through evolution

Scientists classify animals using several different types of data, which include comparing anatomy and physiology, patterns of development, and DNA.

• The animal kingdom is divided in two groups: vertebrates and invertebrates

Section 21. gastrovascular cavity (605)

2. respiration (605)

3. gill (605)

4. open circulatory system (606)

5. closed circulatory system (606)

6. hydrostatic skeleton (607)

7. exoskeleton (607)

8. endoskeleton (608)

9. hermaphrodite (609)

10.external fertilization (610)

11. internal fertilization (610)

Animal Body Systems

Body systems are specialized to carry out different tasks.

Levels of organization:

Cells tissues organs organ systems

organisms

Digestive systems• Simple animals have a gastrovascular

cavity with only one opening, while more-complex animals have a one-way gut.

Respiration/ gas exchange

Simple animals exchange gases directly through their skin.

More-complex aquatic animals use gills, while terrestrial animals use a variety of respiratory organs, such as lungs.

circulatory system

In an open circulatory system, circulatory fluid leaves the vessels and enters the body cavity.

In a closed circulatory system, blood remains in the vessels.

open circulatory system -- primitive system found in insects and crustaceans -- blood not always contained in blood vessels -- heart pumps hemolymph (blood

and cell fluids) into vessels, but vessels empty into large cavities or sinuses

containing organs -- blood diffuses through tissues and back into heart.

closed circulatory system -- found in higher animals -- system is

"closed" because the blood is always contained in vessels.

Nervous SystemWhile simple animals have little coordination

among their nerve cells, complex animals have nerve cords and a brain with associated sensory structures.

Excretory System

For most animals, eliminating wastes is linked to maintaining the correct water balance in their body.

Skeleton/SupportHydrostatic support

Exoskeleton

Endoskeleton

Frog

Asexual

Asexual reproductive methods include fragmentation, splitting in two, and parthenogenesis.

Reproduction that does not involve the fusion of two gametes is called asexual reproduction. A sponge, for example, can reproduce by fragmenting its body. Each fragment grows into a new sponge.

Some species of sea anemone reproduce by pulling themselves in half, forming two new adult anemones

sexual reproduction

In sexual reproduction, male and female gametes combine to form a new individual

Human Reproduction• Eggs produced in the ovary are fertilized in the

fallopian tube and implant in the uterus. Sperm, made in the testes by spermatogenesis, a form of meiosis, must fertilize the haploid egg for it to develop into an embryo.