Introduction to Introduction to AnimalsAnimals

• Chapter 27 Chapter 27

• 1. One characteristic common to all animals is that they are heterotrophicheterotrophic, meaning they must consume food to obtain energy and nutrients.

I. Characteristics of Animals

A. General Features of Animals:

I. Characteristics of Animals

A. General Features of Animals:

• All animals depend either directly or indirectly on autotrophs for food.

• In some animals, digestion is carried out within individual cells; in other animals, digestion takes place in an internal cavity.

2. Mobility-2. Mobility-• Can perform rapid, complex movements

• Move by means of muscle cells, specialized cells that are able to contract with considerable force.

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

• Animals are organisms with ways of moving that help them reproduce, obtain food, and protect themselves.

• Most animals have specialized cells that form tissues and organs—such as nerves and muscles.

3. Multicellularity:3. Multicellularity:

• Animals are composed of cells that do not have cell walls.

• The body size does not matter all of the cells are similar in size.

• Advantage : individual cells can specialize in one life task.

• Meaning adults have two copies of each chromosome.

• One inherited from mother and one from father.

• Only their gametes are haploidhaploid.

• AdvantageAdvantage- is that it permits an animal to exchange genes between the two copies of a set of chromosomes, creating new creating new combinations of genes.combinations of genes.

4. Diploidy4. Diploidy

• Male animals produce sperm cells (which are smaller and have a flagella for moving) and female animals produce egg cells.

5. Sexual Reproduction/Fertilization5. Sexual Reproduction/Fertilization• Most animals reproduce sexually by reproduce sexually by

producing gametes.producing gametes.

• Fertilization occurs when a sperm cell penetrates the egg cell, forming a new cell called a zygote.zygote.

• In animals, fertilization may be internal or external.

• Animals do notdo not have a cell wall.

• This characteristic has allowed animals mobility that other multi-cellular organisms do not have.

• Cells move about in animals bodies all the time.

• Cells called macrophagesmacrophages , act as mobile garbage collectors, crawling over tissues and removing debris.

6. Absence of a Cell Wall6. Absence of a Cell Wall

• The zygote zygote divides by mitosis and cell division to form two cells in a process called cleavage.cleavage.

cleavage

7. Blastula Formation/Cell division7. Blastula Formation/Cell division

• Once cell division has begun, the organism is known as an embryoembryo.

Cell divisionCell division• The two cells that result from cleavage then

divide to form four cells and so on, until a cell-covered, fluid-filled ball called a blastula is formed.

• The blastula is formed early in the development of an animal embryo.

GastrulationGastrulation

• After blastula formation, cell division continues.

• The cells on one side of the blastula then move inward to form a gastrula—a structure made up of two layers of cells with an opening at one end.

• The cells at one end of the blastula move inward, forming a cavity lined with a second layer of cells.

• The layer of cells on the outer surface of the gastrula is called the ectoderm.

• The layer of cells lining the inner surface is called the endoderm.

GastrulationGastrulation

• The ectoderm cells of the gastrula continue to grow and divide, and eventually they develop into the skin, nervous tissue, sense organs such as eyes of the animal.

EctodermGastrulationGastrulation

• The endoderm cells develop into the lining of the animal’s digestive tract and into organs associated with digestion.

Endoderm

GastrulationGastrulation

Formation of mesodermFormation of mesoderm• Mesoderm is found in the middle of the embryo;

the term meso means “middle.”

• The mesoderm is the third cell layer found in the developing embryo between the ectoderm and the endoderm.

Mesoderm

• The mesoderm cells develop into the muscles, circulatory system, excretory system, and, in some animals, the respiratory system.

Formation of mesodermFormation of mesoderm

Fertilization

First cell division

Additional cell divisions

Cell Differentiation in Animal Development

Cell Differentiation in Animal Development

Formation of a blastula

Gastrulation

Formation of mesoderm

Sperm cells

Egg cell

Endoderm

Mesoderm

Ectoderm

• Cells are organized into structural and functional units called tissues. (except in sponges)

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

• Ex: Adipose tissue- store fat

Muscle tissue- contract- producing

movement.

Nerve tissue- conduct signals.

8. Tissue8. Tissue

B. Body SymmetryB. Body Symmetry

• Symmetry is a term that describes the arrangement of body structures.

• Different kinds of symmetry enable animals to move about in different ways.

1 . Asymmetry1 . Asymmetry

• Animals with no symmetry often are sessile organisms that do not move from place to place.

• Most adult sponges sponges have the simplest simplest body form body form and do not move about.

• An animal that is irregular in shapeirregular in shape has no symmetry or an asymmetricalasymmetrical body plan.

AsymmetryAsymmetry

• The bodies of most sponges consist of two layers of cells.

• Unlike all other animals, a sponge’s embryonic development does not include the formation of an endoderm and mesoderm, or a gastrula stage.

2. Radial symmetry2. Radial symmetry

• Animals with radial symmetry can be divided along any plane, through a central axis, into roughly equal halves.

• Radial symmetry is an adaptation that enables an animal to detect and capture prey coming toward it from any direction.

Radial symmetryRadial symmetry

Inner cell layer

• A hydra hydra develops from just two embryonic cell layers—ectoderm and endoderm.

• Most are aquatic, move slowly or drift in ocean currents.

Outer cell layer

3. Bilateral symmetry3. Bilateral symmetry

• An organism with bilateral symmetry can be divided down its length into similar right and left halves.

Bilateral symmetryBilateral symmetry

• In bilateral animals, the anterior, or head end, often has sensory organs.

• The posterior of these animals is the tail end.

• Bilaterally symmetrical animals can be divided in half only along one plane.

• The dorsal, or upper surface, also looks different from the ventral, or lower surface.

Bilateral Symmetry and Body PlansBilateral Symmetry and Body Plans

• All bilaterally symmetrical animals developed from three embryonic cell layers—ectoderm, endoderm, and mesoderm.

• Animals with bilateral symmetry have become specilized in different ways, for example , they have an anterior concentration of sensory structures and nerves, a process called cephalization.cephalization.

• With sensory organs concentrated in the front, such animals can more easily sense food and danger.

• 1. acoelomate-acoelomate- Animals that develop from three cell layers—ectoderm, endoderm, and mesoderm—but have no body cavities .

• They have a digestive tract that extends throughout the body.

C. Internal Body Cavity:C. Internal Body Cavity:

• Some bilaterally symmetrical animals also have fluid-filled spaces inside their bodies called body cavities (coelomcoelom) in which internal organs are found.

AcoelomatesAcoelomates• Flatworms are

bilaterally symmetrical animals with solid, compact bodies. Like other acoelomate animals, the organs of flatworms are embedded in the solid tissues of their bodies.

Acoelomate Flatworm

Ectoderm

Mesoderm

Endoderm

Body cavityDigestive tract

• A flattened body and branched digestive tract allow for the diffusion of nutrients, water, and oxygen to supply all body cells and to eliminate wastes.

Acoelomate Flatworm

Ectoderm

Mesoderm

Endoderm

Body cavityDigestive tract

AcoelomatesAcoelomates

2. Pseudocoelomates 2. Pseudocoelomates

• A roundworm is an animal with bilateral symmetry.

• The body of a roundworm has a space that develops between the endoderm and mesoderm.

Ectoderm

Mesoderm

Endoderm

Body cavityDigestive tract

Pseudocoelomate Roundworm

• It is called a pseudocoelom—a fluid-filled body cavity partly lined with mesoderm.

Ectoderm

Mesoderm

Endoderm

Body cavityDigestive tract

Pseudocoelomate Roundworm

Pseudocoelom

PseudocoelomatesPseudocoelomates

• Pseudocoelomates can move quickly.

• Although the roundworm has no bones, it does have a rigid, fluid-filled space, the pseudocoelom.

• Its muscles attach to the mesoderm and brace against the pseudocoelom.

PseudocoelomatesPseudocoelomates

PseudocoelomatesPseudocoelomates• Pseudocoelomates have a one-way digestive

tract that has regions with specific functions.

• The mouth takes in food, the breakdown and absorption of food occurs in the middle section, and the anus expels waste.

MouthIntestine

Round body shape

Anus

3. Coelomates3. Coelomates• The body cavity of an

earthworm develops from a coelom, a fluid-filled space that is completely surrounded by mesoderm.

• The greatest diversity of animals is found among the coelomates.

Ectoderm

Mesoderm

Endoderm

Body cavity

Digestive tract

Coelomate Segmented Worm

Coelom

• In coelomate animals, the digestive tract and other internal organs are attached by double layers of mesoderm and are suspended within the coelom.

• The coelom cushions and protects the internal organs. It provides room for them to grow and move independently within an animal’s body.

CoelomatesCoelomates

• Segmented animals are composed of a series of repeating, similar units called segments.segments.

• You can observe segmentation in some animals such as earthworms, crustaceans, spiders and insects.

• In vertebrates, segments are not visible externally, but there is evidence in a vertebrae embryo.

• Vertebrae muscles develop from repeated blocks of tissue called somites.somites.

• The backbone consists of a stack of very similar vertebrae.

D. Body SegmentationD. Body Segmentation

• In segmented animals each segment can move independently. However, they are not totally independent of each other because materials pass from one segment to another through a circulatory and nervous system that connects them.

• Therefore, they have great flexibility and mobility.

• Each segment repeats many of the organs in the adjacent segment, as a result an injured animal can still perform vital life functions.

• Segmentation also offers evolutionary flexibility.

Body SegmentationBody Segmentation

• Kingdom Animalia- Kingdom Animalia- contain about 35 major divisions called phyla. (singular Phylum)

• Scientists use a Phylogenetic Tree – Phylogenetic Tree – to show how animals are related through evolution.

• They compare:

• 1. anatomy and physiology

• 2. patterns of development in embryos

• 3. DNA

• The animal Kingdom is often divided into two groups Invertebrates Invertebrates and Vertebrates.Vertebrates.

E. Kinds of AnimalsE. Kinds of Animals

• A. Tissues and Organs – A. Tissues and Organs – have evolved to have evolved to carry out and specialize to perform specific carry out and specialize to perform specific functions. functions.

6 - Important functions of these tissues and

organs are: Digestion

Respiration

Circulation

Conduction of nerve impulses

Support

Excretion

II. Animal Body Systems:II. Animal Body Systems:

a.) Single celled organisms and Sponges digest their food

withinwithin their body cells. intracellularlyintracellularly

b.) Other simple animals digest their food

extracellularlyextracellularly (outside their body cells) within a (outside their body cells) within a digestive cavity. digestive cavity.

• Gastrovascular cavityGastrovascular cavity – – a digestive cavity with only one opening.only one opening. ( hydra and flatworm)

• There can be no specialization within a gastrovascular cavity because every cell in exposed to all stages of food digestion.

c.) Other animals have a digestive tractdigestive tract (gut) withwith two openings,two openings, a mouth and an anus.

• This one way digestive tract allows for specializationThis one way digestive tract allows for specialization. (food storage, breaking down, chemical , absorption.)

1. Digestion1. Digestion1. Digestion1. Digestion

a.) Can take place only across a moist surface, such as

damp skin of an earthworm. (diffusiondiffusion)

b.) Larger, more complex animals have specialized structures.

• gillsgills-very thin projections of tissue that are rich in blood vessels. (provide a large surface area for gas exchange)

• LungsLungs –allow terrestrial animals to respire on dry land.

2. Respiration- 2. Respiration- the uptake of oxygen and the releasethe uptake of oxygen and the release

of carbon dioxide.of carbon dioxide.

2. Respiration- 2. Respiration- the uptake of oxygen and the releasethe uptake of oxygen and the release

of carbon dioxide.of carbon dioxide.

a.) Open Circulatory System- Open Circulatory System- a heart pumps fluid containing oxygen and nutrients through a series of vessels out into the body cavity.

• Fluid washes across the bodies tissues.Fluid washes across the bodies tissues. The The fluid collects in open spaces and flows back to the fluid collects in open spaces and flows back to the heart. Ex: crayfishheart. Ex: crayfish

b.) Closed Circulatory System-Closed Circulatory System-a heart pumps blood through a system of blood vessels.

• The blood remains in the vessels and does not come The blood remains in the vessels and does not come in direct contact with the body’s tissues. in direct contact with the body’s tissues.

• Materials pass into and out of the blood by diffusing through the walls of the blood vessels.

3. Circulation-3. Circulation-transports oxygen and nutrients to transports oxygen and nutrients to

body cells.body cells.

3. Circulation-3. Circulation-transports oxygen and nutrients to transports oxygen and nutrients to

body cells.body cells.

a.) Nerve Cells (neurons) Nerve Cells (neurons) are specialized for carrying messages in the form of electrical impulses. (Conduction)

• These cells coordinate the activities in an These cells coordinate the activities in an animals body. animals body.

• 1. Nerve net- 1. Nerve net- all nerve cells are similar and linked together in a web. (ex: hydra,jellyfish)

• 2. ganglia- 2. ganglia- clusters of neurons that form a brain like structure.( ex: flatworm)

• 3. brains-3. brains- more complex invertebrates have brains with sensory structures, such as eyes, associated with them.

• These cephalized animals interact with their environment in more complex ways. (ex: grasshopper – human)

4. Conduction of Nerve Impulses4. Conduction of Nerve Impulses4. Conduction of Nerve Impulses4. Conduction of Nerve Impulses

• An animals skeleton provides a framework that supports its body and is vital to movement.

a.Hydrostatic skeleton-Hydrostatic skeleton- consists of water that is contained under pressure in a closed cavity. It is formed by the gastrovascular cavity. (ex: hydra, earthworm.)

b.) ExoskeletonExoskeleton- a rigid external skeleton that encases the body of an animal.

• The muscles are attached to the inside of the skeleton, which provides a surface for them to pull against.

5. Support5. Support5. Support5. Support

• Exoskeletons also protect soft body tissues, prevent water loss, and provide protection from predators.

• As an animal grows, it secretes a new exoskeleton and sheds the old one.

• Exoskeletons are often found in invertebrates. An invertebrate is an animal that does not have a backbone.

• C. EndoskeletonEndoskeleton- is composed of a hard material, such as bone, embedded within an animal.

• Invertebrates, such as sea urchins and sea stars, have an internal skeleton called an endoskeleton. It is covered by layers of cells and provides support for an animal’s body.

• The endoskeleton protects internal organs and provides an internal brace for muscles to pull against.

• An endoskeleton may be made of calcium carbonate, as in sea stars; cartilage, as in sharks; or bone.

Calcium carbonate cartilage

• Bony fishes, amphibians, reptiles, birds, and mammals all have endoskeletons made of bone.

bone

• A vertebrate is an animal with an endoskeleton and a backbone. All vertebrates are bilaterally symmetrical.

• 6. Excretion-6. Excretion- the removal of wastes produced by cellular metabolism. (ammonia)

• a.)Diffusion-through skin or gillsa.)Diffusion-through skin or gills (fish and some aquatic invertebrates)

• This is effective but they lose a lot of water.

• Terrestrial animals need to minimize water loss- they do so by:

• b.) Converting ammonia to nontoxic b.) Converting ammonia to nontoxic chemicals, like urea.chemicals, like urea.– Water and other useful substances are returned to

the body in this process.

– Kidney’sKidney’s filter fluid from the blood and excrete them as concentrated urine.

• B Reproductive StrategiesB Reproductive Strategies

• 1. Asexual Reproduction- 1. Asexual Reproduction- does not involve the fusion of two gametes.

• a.) fragments-ex: starfish and sponges

• b.) fission- sea anemone

• c.) parthenogenesis- in which a new individual develops from an unfertilized egg. (ex: honeybees, a few species of fish, amphibians and lizards.)

• 2. Sexual Reproduction- 2. Sexual Reproduction- a new individual is formed by the union of a male and a female gamete.

• Testes- produce the male gametes (sperm)

• ovariesovaries- produce the female gametes (egg)

• Hermaphrodites-Hermaphrodites- have both (ex; earthworm, some fish, slugs.

• a.) External fertilization- External fertilization- the egg is fertilized the egg is fertilized outside the female body. outside the female body.

– Large numbers of gametes are released due to % Large numbers of gametes are released due to % that actually get fertilized.that actually get fertilized.

– Ex: fish Ex: fish

• b.) Internal fertilization- Internal fertilization- the union of the sperm and egg occurs within the female’s body.

– the male places semen directly into the the female’s body.

– In this way fertilization takes place in a moist environment, and the gametes are protected from drying out.

– All developing eggs must be kept moist.

•