Chapter 26

Introduction to Introduction to AnimalsAnimals

Characteristics of Characteristics of AnimalsAnimalsCh. 26 Sec. 1

Characteristics of Animals

1. Multicellular Organization

Animal bodies contain many cells.

Adult humans have ~ 50 trillion cells!

Cells do not have a rigid cell wall.

Almost all animals have cell specialization.

There is a division of labor; different types of cells do different jobs.

Groups of cells take on special shapes and functions in order to work together and can not survive long without all the other cells in the body doing their jobs.

Most have different tissue types that make up organs.

Characteristics of Animals2. Heterotrophy

Animals must ingest food for energy.

After eating, animals must digest food inside their bodies.

Carbohydrates, lipids, amino acids, etc. are broken down and used.

The lives of animals are connected - they all rely on other living things to survive.

Example: food-web

Because animals must obtain food from other sources, they are able to move around their environment in search of food.

Characteristics of Animals3. Sexual Reproduction and Development

Most animals reproduce sexually.

Parents recombine genes to form genetically unique offspring.

During development, a fertilized egg must somehow develop into an adult form.

There are many different ways to do this.

Development is one of the most complicated biological processes known!

Characteristics of Animals4. Movement

Most animals move about their environment.

Movement requires two animal-specific tissue types – nerves and muscles.

Advantages of movement – find food, find new environment, and avoid predators.

Kinds of Animals Animals: are multicellular heterotrophs that lack cells

walls.

There are two main groups:

1. Invertebrates – those without a backbone

These make up 95% of all living animal species today.

Land invertebrates are quite small because they lack internal skeletons for support.

Ocean invertebrates can grow extremely large – 42ft. Giant squid.

The largest structure built by organisms is actually the Great Barrier Reef made of coral.

Examples: worms, bugs, lobsters, clams, sponges, squids, and slugs.

Kinds of Animals2. Vertebrates – those with a backbone.

These animals are more familiar to us.

The skeleton and backbone provide support and aids in movement.

We call organisms with a backbone – Chordates

Skeleton is composed of bone or cartilage.

Examples: fish, amphibians, reptiles, birds, and mammals

Animal Body SystemsCh. 26 Sec. 2

Support One of the keys to the success of

animals is their ability to move. This would not be possible without a skeleton.

Three types of skeletons:

1. Hydrostatic

2. Exoskeleton

3. Endoskeleton

Skeleton Types1. Hydrostatic: a cavity that is filled with water and

has support functions.

Ex: jellyfish and worms

2. Exoskeleton: hard external, supporting structure that encloses the body.

Ex: insects, clams, crabs, and spiders

3. Endoskeleton: an internal skeleton made of bone and cartilage.

Ex: humans, lizards, fish, and birds

Digestive and Excretory Systems

Digestive System: this is responsible for extraction of energy and nutrients from an animal’s food.

Single-celled organisms and sponges do not have digestive systems. They absorb food through the body cells.

All other animals digest their food outside of their body cells and within a digestive cavity.

○ Simple animals have a gastrovascular cavity.

○ Gastrovascular cavity: a cavity that serves as both a digestive and excretory purpose.

Has only one opening!

○ Digestive tract: two openings (mouth and an anus) and allows for specialization and more efficient digestion.

Digestive and Excretory Systems Excretory System: removes waste products from an animal’s

body.

Waste products are produced by cellular metabolism.

As the excretory system eliminates the wastes, water and other useful substances are returned to the body.

Waste products such as ammonia will hurt or kill animals.

○ Aquatic (water) animals excrete ammonia through their skin and gills. Results in water loss.

○ Terrestrial (land) animals need to minimize water loss, so most animals convert ammonia into less toxic urea. Then passing it through the body.

Nervous System Nervous system: this system carries information about the environment

through the body and coordinates responses and behaviors.

Nerve net: nerves cells do not coordinate actions efficiently. Ex: hydra

Simple nervous systems are a group of cells working together as a collection to carry electrical impulses throughout an animal’s body.

○ Ganglia: a cluster of nerve cells that can coordinate responses (simple brain).

○ Ex: flatworm

Complex nervous systems are more common in complex animals.

○ They will have a true brain and other sensory structures such as eyes.

○ They are also capable of sophisticated behaviors.

○ Ex: humans, dogs, cats, horses

Nervous Systems

Circulatory SystemCirculatory System: transports blood, gases, nutrients, and other

substances within the body.

Open circulatory system: heart pumps fluid containing oxygen and nutrients through a series of vessels into the body cavity.

Closed circulatory system: heart pumps blood through a system of vessels. These vessels from a network that allows blood to flow back to the heart.

Respiratory Systems Respiratory System: responsible for

exchanging oxygen and carbon dioxide between the body and the environment.

Most animals have specialized respiratory systems.

Aquatic (water) animals – gills

○ Ex: fish, salamanders, and sharks

Terrestrial (land) animals – lungs or some form

○ Ex: cats, dogs, humans, etc.

Reproductive Systems Reproductive Systems: to produce offspring

and keep the species going.

Two Types:

1. Asexual: when an individual produces exact copies of itself.

sea star – grow new body from one arm

Salamanders – new individual from unfertilized egg

2. Sexual: when a new individual is formed by the union of male and female gametes.

Ex: cats, dogs, horses

Evolutionary Trends in AnimalsCh. 26 Sec. 3

Tissues and Symmetry Through evolutionary time, animals have

developed more complex body plans, including true tissues and bilateral symmetry.

Tissues: the cells of animals except sponges are organized into units called tissues.

○ Groups of cells that have the same structure and work together to perform a specific function.

Ex: muscles and skin

Symmetry: describes how an animal’s body can be divided into similar pieces.

Types of Symmetry1. No Symmetry

(asymmetrical): these animals have irregular bodies with no alike parts

Ex: sponges

2. Radial Symmetry: similar parts branch out from a central line (like spokes of a bike).

Ex: sea anemones, jellyfish, and hydras

Types of Symmetry3. Bilateral Symmetry: similar parts

are on the right/left, top/bottom, front/back ends.

Ex. Mammals

Allows parts of the body to become specialized in different ways.

Most bilaterally symmetrical animals have an concentration of sensory structures and nerves toward the “head” called cephalization.

Ex: brain

Let’s Compare!

Embryo Development During embryo development, germ layers are formed.

Germ Layers: are fundamental tissue types found in all animals (except sponges).

Three Types:

1. Ectoderm: outer germ layer

2. Mesoderm: middle germ layer

3. Endoderm: inside germ layer

Body structures develop from these layers.

Types of Germ Layers Cnidarians and

ctenophores have only 2 germ layers

Ex: hydras, jellyfish

All other animals have 3 germ layers.

Ex: humans, cats, worms

Body Cavities

Most animals have internal body plans.

Body cavity: space inside of the body.

The body cavity can aid in movement, act as a reservoir, house organs, ect.

The specific cavities depend upon the animal.

Animal Diversity Animals that are similar in shape and body types are

usually assumed to be closely related.

Note: this is not always the case, as in sharks and dolphins.

Three animal divisions:

1. Invertebrates: there is a wide range of body symmetry and complexity, but all lack a backbone.

2. Chordates: they have a notochord (strong, flexible fiber in their back) at some point.

3. Vertebrates: they have a spinal cord and backbone.