animals

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Introduction to Animals

The first animals probably arose from the sea.

Taxonomists have grouped animals into several phyla based on evolutionary relationships.

Many taxonomist recognize 30 or more animal phyla. We will investigate 11 phyla. Ten of the phyla include invertebrates and only Chordata includes the vertebrates.


Origin and Classification

Kingdom Animalia

Animals are capable of more complex and rapid movements compared to other kingdoms.

Evolved from heterotrophic protists

Most animals contain large numbers of cells.

Humans contain 50 trillion cells.

DNA is the most direct evidence of evolutionary relationships between animals


Characteristics of Kingdom Animalia

Multicellular Organization

Cells without cell walls

Heterotrophic

Sexual reproduction and development

Movement


Multicellular Organization

Most important advantage of multicellularity:

Individual cells can specialize in one life task.

In most animals, there is a division of labor.

Specialization is the adaptation of a cell for a particular function.

Tissues are the organization of similar cells.

Specialized cells can carry out their tasks

more effectively than cells that must do many tasks.


Animals are Heterotrophic They must obtain complex organic material from other sources.

Most accomplish this through ingestion.

Digestion is accomplished within the animal. This process extracts the carbohydrates, protein and lipids from the food eaten.


Functions as a mechanism for breaking down food into small molecules

Single-celled organisms digest food within their body cells


Digestion

Choanocytes (specialized cells) capture & digest food for sponges

Two types:

Two-way digestive system

One opening in for food to enter & leave

One-way digestive system

have a mouth and an anus

Food enters the mouth, continues in one direction through the digestive tract, and wastes leave through the anus

Includes annelids, arthropods, & vertebrates


Digestive Systems

Sexual Reproduction

Requires two parents

Gametes are haploid

Allows for genetic variation

Most animals reproduce sexually using internal fertilization

Asexual Reproduction

Only one parent

Produces offspring genetically identical to the parent

Parthenogenesis:

The eggs develop without being fertilized

New offspring will be all female

occurs in some fishes, several kinds of insects, and a few species of frogs and lizards

Female bees can reproduce both sexually and asexually.

Hermaphroditic organisms produce both eggs and sperm,

but cannot fertilize their own eggs.


Reproduction

In most animals, the gametes are the ONLY haploid cells in the life cycle.

Sexual reproduction restores the diploid number and increases genetic variation.

During the developmental process, the zygote undergoes many mitotic divisions. These identical cells must undergo differentiation.

Differentiation is process of cell becoming different from each other and being specialized.


Sexual Reproduction and Development

Movement Most animal are able to move.

The ability to move results from the interrelations of two types of tissues found only in animals: nervous tissue and muscular tissue.

There are a few animals that are sessile (immobile).


SESSILE SEDENTARY

MOTILE

Sponge Chiton

Cheetah


Oxygen and nutrients are transported

Two types:

Open circulatory system

Body tissues are bathed directly in fluid containing oxygen

Closed circulatory system

The blood always remains inside the blood vessels and never comes in direct contact with the cells.

The materials enter and exit the blood vessels through the walls


Circulatory System

Have some type of skeletal support

Endoskeleton inside and made of cartilage &/or bone

Grow inside the animal

Exoskeletons found in arthropods

Hard and encases the body

Cover the outside of the body

Limit size

Must be molted making animal vulnerable to predators

Hydrostatic skeletons: fluid-filled internal cavities

Worms and echinoderms (starfish)


Support System

Taking in O2 & releasing CO2

Gases can diffuse across moist surfaces (earthworms)

Gills filter O2 from water (aquatic animals)

Lungs take O2 from air (terrestrial animals)

Lungs

Gills


Respiratory System

http://www.biology-resources.com/drawing-fish-swimming.html

http://www.biology-resources.com/drawing-fish-swimming.html

Coordinates the activities of the animal’s body

Neurons – nerve cells that transmit electrochemical signals

Nerve net - network of neurons, very little coordination

Ganglia – clusters of neurons; may serve as a simple brain in anterior end of an animal

Brain – control center at anterior end


Nervous System

Invertebrates

10 phyla

95% of animals

Chordates

Notochord

Dorsal nerve cord

Pharyngeal pouches

Postanal tail

Vertebrates

Include fishes, birds and mammals

Kingdom

Animalia

Invertebrates Chordates

Vertebrates


Animal Diversity

Atom Molecule or compound Organelle

CELLLevels of Organization

Tissue

Organ

Organ system Organism

Life begins


Sponges are the ONLY animals that have just the cellular level

All other animals show these levels – cell, tissue, organ, and system

Cells may specialize (take own different shapes and functions)

Cells are held together by cell junctions to form tissues


Levels of Organization

What is the difference in a vertebrate and an invertebrate?

A vertebrate is an animal with a backbone and invertebrates do not have a backbone.


Animal Body Structure

Symmetry

Germ layers

Body Cavities


Symmetry refers to the consistent overall pattern of structure of an animal.

Animals have three patterns of symmetry.

Asymmetry – no symmetry

Radial Symmetry – similar parts branch in all directions from a central point

Bilateral Symmetry- similar halves on either side of a central plane. (distinct left and right halves)


Symmetry


Patterns of Symmetry

Bilateral

Bilateral

Radial

Radial


Identify the Type of Symmetry

Most animals have a dorsal, ventral, anterior and posterior side or orientation.

Dorsal – top

Ventral – bottom

Anterior – head

Posterior - tail

Most animals exhibit cephalization, the concentration of sensory and brain structures in the anterior. Animals with cephalization have a head!


Directional Terms

Germ layers are fundamental tissue types found in

all animals except sponges (no true tissues).

Ectoderm: becomes skin and nervous system

Mesoderm: forms liver and lungs

Endoderm: forms muscle and other systems


Germ Layers

Body Cavities

COELOM : a fluid filled space that forms between the digestive tract and the outer wall of the body during development.


Acoelomate: no body cavity

Pseudocoelomate: fluid-filled cavity

Coelomate: defined cavities


Types of Body Cavities

2 germ layers

Ectoderm and endoderm

not separated by a cavity

least complex body plan

Examples: sponges and cnidarians

3 layer acoelomate

endoderm, mesoderm and ectoderm

not separated by a cavity

Examples: flatworms


Acoelomate (without a coelom)

Pseudocoelom: fluid filled cavity between the gut and body wall

Cavity formed between mesoderm and endoderm

Body cavity only partially lined with mesoderm

Examples: roundworms and rotifers


Pseudocoelomate

Cavity completely lined with mesoderm

Most complex body plan

Examples: mollusks, annelids, arthropods, echinoderms, and chordates

Similar to human body plan


Coelomate

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