What is an Animal?

Chapter 25

Characteristics of Animals

Animals obtain food Sessile – Organisms that are permanently

attached to a surface Sessile animals filter feed Sessile animals are aquatic

Characteristics of Animals

Animals digest food Multicellular organisms digest food in a digestive

tract

Characteristics of Animals

Animal cell adaptations Animal cells are differentiated and carry out

different functions

Development of Animals

Fertilization The fusing of a sperm

cell to an egg cell Gamete – a sex cell Zygote – a fertilized egg

(2n)

(n)

(n)

Cell Division

Zygotes divide by mitosis Once cell division had begun, the organism is

known as an embryo Blastula – a fluid-filled ball covered with cells

(2n)

Gastrulation

Gastrula – the cells on one side of the blastula move inward

Animal Reproduction

Asexual reproduction – requires only one parent Ex. – bacteria

Sexual reproduction – requires two parents

Reproduction

Asexual Sexual

External fertilization

Internal fertilization

Animal Reproduction

Internal fertilization – sperm and egg unite inside the body

External fertilization – sperm and egg unite outside the body

Reproduction

Asexual Sexual

External fertilization

Internal fertilization

Animal Reproduction

External fertilization occurs in water Pro: Many offspring can be produced Con: Parental protection is reduced

Animal Reproduction

Internal fertilization occurs inside animals Pro: Increased parental protection Con: Low number of offspring produced

Directional Terms

Superior – Above; over Inferior – Below; under

Directional Terms

Anterior– Toward the front Posterior– Toward the backside

Directional Terms

Dorsal – Near the upper surface, toward the backbone

Ventral – Toward the bottom, towards the belly

Directional Terms

Medial – Toward the midline of the body Lateral – Away from the midline; the outer

side of the body

Directional Terms

Proximal – Close to Distal – Far from

Directional Terms

Cephalic (or cranial) – Towards the head Caudal – Towards the tail

Directional Terms

Superior Inferior

Anterior Posterior

Dorsal Ventral

Medial Lateral

Proximal Distal

Cephalic Caudal

Directional Terms

Symmetry

Asymmetry – an animal that has no symmetry Example: sponge

Symmetry

Radial symmetry – divided along a plane, through a central axis, into roughly equal halves

Symmetry

Bilateral symmetry – divided down its length into similar right and left halves

Body Cavities

Coelom – cavity Cavity – an empty space Body cavities make it possible for animals to

grow larger

Three body cavities1. Acoelomates – animals that develop from three cell layers but have no body cavities

Body Cavities

2. Pseudocoelomates – a fluid-filled body cavity partly lined with mesoderm

Pseudocoelomate animals are larger and thicker than acoelomate animals

Body Cavities

3. Coelomates – a fluid-filled space that is completely surrounded by mesoderm More complex animals are coelomates

Animal Protection and Support Exoskeleton – a hard covering on the outside

of the body that provides a framework for support

Crayfish

Animal Protection and Support Endoskeleton – an internal skeleton within

animals

Animal Protection and Support Invertebrate – an animal without a backbone Vertebrate – an animal with a backbone

Animal Classification

Animals

Invertebrates

Vertebrates

SpongesCnidariansWormsMollusksArthropodsEchinoderms

Ectotherms(cold-blooded)

Endotherms(warm-blooded)

FishesAmphibiansReptiles

BirdsMammals