Ch17_Animals

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Multicellular eukaryotes

AnimalsDomain

Domain

Domain

Kingdoms

Nutritional mode:

Level of organization:

Cells

Cells organized in tissues

Motile

What is an animal?

Main differences with plants

Nutritional mode: Heterotrophic (Ingestive)

Level of organization: Multicellular

Cells without cell wall

Cells organized in tissues, organs, and organ systems

Nervous tissue and muscle tissue, are unique to animals

Bodies are held together by structural proteins such as collagen

Motile (They move!) at least in part of their life cycle

Main differences with fungi

Most animals:

Are diploid (2N)

Reproduce sexually

Proceed through a

series of typically similar

developmental stages

Animal development

A larva (pl. larvae) is a

juvenile, young stage in the

development of animals

(examples: fish, tadpoles,

most aquatic animals)

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What is used to classify animals?

General features of body

structure and embryologic

development

More recently, using

genetic data

(1) Sponges are different from all

other animals becausespongeslack true tissues and organs

(1)

(2)

(2) Body symmetry.

Radial symmetry

refers to animals that are

identical all around a

central axis, where the

mouth is located.

Bilateral symmetry exists where there is only

one way to split the animal into equal halves.

What is used to classify animals?

(3) The presence or not of a Body cavity,

called coelom, a fluid-filled space

separating the digestive tract from the

outer body wall

(4) Most animals have three germ layers (group of cells, formed during animal

embryogenesis)…

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Really adapted to land (but not all of them are terrestrial!)

Aquatic Mostly Aquatic, Some parasites

Most animals are aquatic!

Some facts about animals

Animals in the ocean do not

require mechanisms to deal

with rapid or extreme changes

in the environment

Stable properties

No risks of dehydration

Ion contents in sea similar to

cytoplasm: osmotic balance

Why is living in the ocean

“better”?

Insects: 65% of the animal diversity on Earth

95% of all animal species are invertebrates

(animals without a backbone)

Phylum Chordata: Includes the vertebrates (Fish, Amphibians, Reptiles, Birds, Mammals)

(1) Sponges (Phylum Porifera)

Simplest body plan: No true tissues. A

few cellular types

No symmetry: Asymmetric

Adults are sessile (permanently attached)

Feeding by filtering water

Sexual reproduction: external

fertilization and a free-swimming

larval stage

Asexual reproduction by

fragmentation or budding is very

common

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(jelly fishes, sea anemones, corals)

Medusa (motile) Polyp (attached)

Two basic forms:

2) Radial symmetry

Parts of the body

radiate from the center,

where the mouth is

located

(2) Cnidaria 1) Evolution to true tissues with different functions

Nervous tissue

Reproductive tissue

Digestive tissue

3) They have tentacles

with stinging cells

Incomplete digestive systemOnly a mouth/anus surrounded by tentacles

Polyp

Medusa

Reproduction

Some show alternation of generations like in some

plants (sexual/asexual)

Asexual reproduction produces jellyfishes or

polyps (motile), by fragmentation or budding

Sexual reproduction produces polyps (sessile)

Stinging cells Cnidarians are carnivores that use tentacles, armed with cnidocytes (“stinging cells”), to capture prey

Informal classification

Corals

Sea anemones

Jellyfish

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(3) Flatworms (Phylum Platyhelminthes)

Sexual reproduction becomes dominant, though some

(e.g. planarian) reproduce asexually by fragmentation

The first and simplest bilateral animals

First group to show a central nervous system, that appeared

connected with bilaterally

Better to swim or crawl in one direction!

Allow animals to be more active when hunting

More sophisticated behaviors are possible

Some are free-living, many are parasites with two different types of hosts

Parasitic flatworms are Flukes and Tapeworms

Flukeworms: Two hosts: one vertebrate and one invertebrate

• Larva invertebrate, Adult parasite vertebrate

Tapeworms: Two hosts: two vertebrates.

• Larva herbivore, Adult parasite carnivore

Larval stage infects an

invertebrate host

Schistosomiasis: (fluke) diarrhea, liver damage, anemia, lowering of the body’s

resistance (2nd most important disease caused by parasites after malaria)

Adult parasite

infects a

vertebrate host

Blood flukes reproduce

sexually in the human host.

The fertilized eggs exit the

host in feces.

The eggs develop in water

into ciliated larvae. These

larvae infect snails, the

intermediate hosts.

Asexual reproduction

within a snail results in

another type of motile

larva, which escapes

from the snail host.

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(4) Molluscs (Chitons, Snails, Slugs, Clams, Squids, Octopi)

A Soft body, often covered with a shell, composed of one

or more plates is characteristic of this group

Most mollusks have all organs systems present, including

Circulatory and respiratory system

Bilaterally symmetrical, body divided in three main parts:

A muscular foot used for movement

A visceral mass housing most of the internal organs

A mantle, which secretes the shell if present

Radula as a

feeding organ is

unique to many

mollusks

Sexual Reproduction, with

separate sexes

A larval and free-swimming stage

(trocophore) develops in the adult form

GastropodaSnails, Slugs,

Limpets,

Abalones

BivalvesClams, Mussels, Oysters, etc

Filter feeders (fitler the water to get the food)

The mantle cavity of a bivalve contains gills that are

used for feeding as well as gas exchange

Carnivores with beak-like jaws

surrounded by tentacles of their

modified foot

CephalopodaSquids, Octopuses, Nautilus

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(5) Round worms (Phylum Nematoda)

Cylindrical in shape, tapered at both ends

Tough cuticle covers the body

Sexual reproduction, with separate sexes

•The amount of damage is often

proportional to the number of roundworms

• Slight infestation: anemia,

• Heavy infestation: mental or physical

retardation

Most are free-living, mostly in the sediments, being important

decomposers

Some are harmful parasites in plants or vertebrates

2) First animals having a real body cavity (coelom), not

filled with fluid, the organs are located in the cavity

(6) Segmented worms (Phylum Annelida)

1) First animals with real body segmentation

Body organized in compartments or segments

Sexual reproduction, usually with separate sexes

Most annelids have all organs systems present, including

Circulatory and respiratory system

The three main groups of annelids are:

Earthworms, which eat their way through soil

Polychaetes, marine worms with segmental appendages for movement and gas exchange

Leeches, typically aquatic free-living carnivores but with some bloodsucking forms

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(7) Arthropoda

The most diverse and successful animal group has…

1) their body segmentation

2) hard exoskeleton

3) and jointed appendages

Exoskeleton: Made of chitin (same stuff that makes cell

walls in fungi!)

Provides protection and

Points of attachment for muscles that move appendages

Sexual reproduction,

with separate sexes

All arthropods have all organs systems present, including circulatory

and respiratory system

Does not grow with the individual and must be replaced as

the animal increases its size: molting

(Crustaceans, Insects, Spiders, Scorpions,

Centipedes, Millipedes, Ticks, Mites)

Insects make 65% of animals on Earth

Arachnids

Live on land

Have 4 pairs of walking legs

+ pair of feeding appendage

no antennae

Crustaceans

Are nearly all aquatic

Have multiple pairs of specialized

appendages, two pairs of antennae

Millipedes and Centipedes

Millipedes eat decaying plant matter

Have two pairs of short legs per body segment

Centipedes are terrestrial carnivores with poison claws

Have one pair of short legs per body segment

Insects

Insects live on land, freshwater, and the air!

Have 3 pairs of walking legs, one pair of antennae

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(Sea stars, Sea urchins, Sea cucumbers, Brittle

stars)(8) Echinoderms

1) Radial symmetry in the adult form

No head and tail, or left and right side present

Body parts radiate from the center

Bilateral symmetry during the larval stage

2) Endoskeleton, hard plates just below the skin

Sexual reproduction, with separate

sexes

3) Also unique to echinoderms is a water vascular system and tube feet for locomotion

(9) Chordata All chordates share during embryology…

1) Notochord: flexible rod Gives origin to the backbone

1) 2)

2) Dorsal, hollow nerve cord CNS (brain + spinal cord)

3)

3) Pharyngeal slits Gills in aquatic vertebrates. Parts of the

ear, head, and neck in terrestrial ones

4)

4) Post anal tail

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Are fish that…

Have a cranium

and rudimentary

vertebrae

But lack jaws

and paired fins

All ectoparasites

Lampreys

lamprey

Chordates consists of three groups of invertebrates:

Lancelets are bladelike animals without a cranium.

Tunicates, or sea squirts, also lack a cranium.

Hagfishes are eel-like forms that have a cranium.

All other chordates are vertebrates, which show segmentation

in the backbone and muscles

hagfish

Hagfish

slime

Gills for gas exchange

External fertilization

Soft shelled eggs

Fish The two main groups are

cartilaginous and bony fish

Have jaws and paired fins

Are the most diverse group

of vertebrates

Amphibians Includes frogs, toads, salamanders

Were the first tetrapods (vertebrates with 4 legs)

Wet skin (not adapted to live in dry environments)

Lungs (not fully functional) and skin for gas exchange

External fertilization

Soft shelled eggs

Still need to back to

the water for reproductionTadpole (larva)

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Waterproof skin

Internal fertilization

Hard shelled and amniotic eggs Have mammary glands that produce milk,

which nourishes the young

Have hair

Most develop the embryo inside the mother

ReptilesAre the first vertebrates to be

fully adapted to land

BirdsAre very modified reptiles

that have in addition unique

adaptations for flying

Hollow bones

Feathers

Forelimbs modified as wings

Mammals

The Amniotic Egg

Is the sac in which the fetus

develops in amniotes. It is a

tough but thin transparent pair

of membranes, which hold a

developing embryo until

shortly before birth

Ch.21

The placenta, which helps in nutrition and gas

exchange, includes the…

The amniotic sac, that has the amniotic fluid

and the embryo

Blood from the embryo travels to the placenta

through arteries of the umbilical cord and returns

via the umbilical vein

In mammals…

(Water-filled membrane,

protection and moisture)

AMNION

In reptiles and birds…

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Skeleton

Many animals have some type of

support system or skeleton. Skeletons

serve as:

Protects the animal

Provides points of attachment

for muscles

Does not grow with the individual

and must be replaced as the animal

increases its size

Endoskeleton:

internal skeleton

present in

vertebrates and

some

echinoderms

Exoskeleton: external skeleton

present in arthropods

Chitin insects, spiders,

scorpions, centipedes,

millipedes

Add calcium! crustaceans

Temperature regulation

Ectotherms:

Animals cannot regulate the body temperature

Regulate their temperature by moving

from one place to another:

• all others

Have internal temperature-regulating

mechanisms:

• birds and mammals

• Able to adapt to any environment

• But with a very high metabolism

(energy use)

Homeotherms:

• Animals that maintain a constant

body temperature, generally

higher than the environmental

temperature