Ch17 Animals - Jocha-Biologyjocha-biology.net/handouts/gralbio/Animals.pdfMost mollusks have all organs systems present, including Circulatory and ... body divided in three main ...

Ch17_Animals

� 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)

Ch17_Animals

What is used to classify animals?

Biologists categorize animals by:

� General features of body

structure and embryologic

development

� More recently, using

genetic data

(1) Sponges are different from all

other animals because, spongeslack true tissues and organs

(1)

(2)

(2) Body symmetry.

� Radial symmetryrefers 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)…

Ch17_Animals

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 with 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

Ch17_Animals

(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

Ch17_Animals

Ch 7(3) Comb jellies (Phylum Ctenophora)

� Radial symmetry like in cnidarians, but comb jellies have…

1. A radially arranged rows of ciliated plates for swimming

2. Tentacles not in whorls around the mouth,

3. Adhesive cells for food capture and the NO stinging cells

4. An aboral (top) sense organ

� Swim with eight rows of ciliary combs

� long cilia fused at the base

Continuous beating refracts light,

creating a prism-like multicolor effect

(4) Flatworms (Phylum Platyhelmithes)

� 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

Ch17_Animals

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.

(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

Ch17_Animals

(6) 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 is

unique to

mollusks: Ribbon

of small teeth

used to feed

� 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

Ch17_Animals

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

filled with fluid, the organs are located in the cavity

(7) Segmented worms (Phylum Annelida)

� 1) First animals with real body segmentation

� Body consists of a series of similar 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 free-living carnivores but with some bloodsucking forms

(8) Arthropoda

� The diversity and success of arthropods are largely due to

1) their body segmentation

2) hard exoskeleton

3) and jointed appendages

� Exoskeleton: external skeleton present in arthropods is 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

Ch17_Animals

Arachnids

� Live on land

� Have 4 pairs of walking legs

and a specialized pair of

feeding appendages, 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

(Sea stars, Sea urchins, Sea cucumbers, Brittle

stars)(9) Echinoderms

1) Pentaradial 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

� A network of hydraulic canals branching into

tube feet that function in locomotion, feeding,

and gas exchange

Ch17_Animals

(10) Chordata All chordates share during embryology…

1) Notochord: flexible rod � Gives origin to the backbone

1) 2)

2) Dorsal, hollow nerve cord � Central nervous system (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

� 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

Ch17_Animals

� 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)

� 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

Reptiles� Are the first vertebrates to be

fully adapted to land

Birds� Are very modified reptiles

that have in addition unique

adaptations for flying

� Hollow bones

� Feathers

� Forelimbs modified as wings

Mammals

Ch17_Animals

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…

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 roundworms and

arthropods

Chitin � insects, spiders,

scorpions, centipedes,

millipedes

Add calcium! � crustaceans

Ch17_Animals

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 / Endotherms:

• Animals that maintain a constant

body temperature, generally

higher than the environmental

temperature