biol 108 chp 11-pt 1: animal diversification

Chapter 11Chapter 11 Part 1Part 1

Animal DiversificationAnimal Diversification

BIOL BIOL 108 108 Intro to Bio Intro to Bio SciSci

Rob Rob SwatskiSwatski Assoc Prof Assoc Prof BiologyBiology

HACCHACC--YorkYork

11·1–11·3 Animals are

just one branch of the

Eukarya domain.

11.1 What is an animal?11.1 What is an animal?

Three Key Characteristics

Take-Home Message 11.1

Animals are organisms that share three characteristics:

1) All of them can move during at least one stage of development.

2) All of them eat other organisms.

3) All of them are multicellular.

11.2 Four key distinctions 11.2 Four key distinctions divide the animals.divide the animals.

1) Does the animal have 1) Does the animal have defineddefined tissuestissues, with specialized cells?, with specialized cells?

2) Does the animal develop with 2) Does the animal develop with radial symmetry or bilateral radial symmetry or bilateral

symmetry?symmetry?

A body structured like a pie or

A body with a left and right side, which are mirror images

3) During development, does 3) During development, does the animal’s gut develop from the animal’s gut develop from front to back or back to front?front to back or back to front?

Protostomes

and

Deuterostomes

4) Does growth occur by 4) Does growth occur by molting or by adding molting or by adding

continuously to the skeletal continuously to the skeletal elements? elements?


The animals probably originated from an ancestral protist.

Four key distinctions divide the extant animals:

1) Tissue or not

2) Radial or bilateral symmetry

3) Protostome or deuterostome development

4) Growth through molting or through continuous skeletal enlargement

11.3 Everything that is not 11.3 Everything that is not extinct is evolutionarily extinct is evolutionarily

successful.successful.

What is “success” evolutionarily?What is “success” evolutionarily? Extant or Extinct


From an evolutionary perspective, all extant species are successful.

However, some groups are represented by more species than others.

Among the 36 animal phyla, 9 phyla account for more than 99 percent of all described animal species.

11.4 Invertebrates are animals without a backbone.

11.4 11.4 Invertebrates are the largest Invertebrates are the largest and most diverse group of animals.and most diverse group of animals.


Invertebrates, defined as animals without a backbone, are the largest and most diverse group of animals, comprising 96% of all the living species of animals.

The invertebrates are not a monophyletic group, however, and include protostomes and deuterostomes.

11.5–11.12 Across

several evolutionary transitions, the

invertebrate animals diversified.

11.5 Sponges are animals that 11.5 Sponges are animals that lack tissues and organs.lack tissues and organs.

Sponge ReproductionSponge Reproduction

How do they do it?

Hermaphrodites

• Male and female sexual reproductive organs

• Free-swimming larvae become sessile adults

Asexual reproduction

• Budding


Sponges are among the simplest of the animal lineages.

A sponge consists of a hollow tube with pores in its wall, it has no tissues or organs, and only three kinds of cells.

11.6 Jellyfish and other cnidarians 11.6 Jellyfish and other cnidarians are among the most poisonous are among the most poisonous

animals in the world.animals in the world.

Cnidarians Cnidarians

Two types of cnidarian bodies:

• A sessile polyp

• A free-floating medusa

Reproduce both sexually and asexually

Carnivores that use cnidocysts

• Stinging cells

3 Major Groups of Cnidarians3 Major Groups of Cnidarians

Corals

Sea anemones

Jellyfishes

The CoralsThe Corals

Small, soft-bodied polyps living in large colonial groups

Secrete calcium carbonate

Stinging tentacles surrounding a mouth

Sexual and asexual reproduction

How is global warming affecting the How is global warming affecting the coral reefs of the world?coral reefs of the world?

The Sea AnemonesThe Sea Anemones

Resemble flowers

Free-swimming larval stage

Adult stage settles

• But may crawl slowly

The JellyfishesThe Jellyfishes

Range tremendously in size

Some species deadly


Corals, sea anemones, and jellyfishes are radially symmetrical animals with defined tissues, in the phylum Cnidaria.

All cnidarians are carnivores and use specialized stinging cells located in their tentacles to capture prey.

11.7 Flatworms, roundworms, and 11.7 Flatworms, roundworms, and segmented worms come in all segmented worms come in all

shapes and sizes.shapes and sizes.

Annelids: Annelids: PolychaetesPolychaetes

Marine worms

“Many bristles”

Some are burrowing.

Some are tube dwelling.

Annelids: EarthwormsAnnelids: Earthworms

“Few bristles”

Bulk feeders

• Consume particles of soil and organic material

Castings are valued by gardeners.

Annelids: LeechesAnnelids: Leeches

The saliva of blood-sucking leeches contains an anticoagulant substance that prevents blood from clotting.

Not all leeches are blood suckers.

• More than half the species of leeches are predators.


Worms are found in several different phyla and are not a monophyletic group.

All are bilaterally symmetrical protostomes with defined tissues.

The flatworms and segmented worms (annelids) do not molt; the roundworms do.


Flatworms include parasitic flukes and tapeworms, many of which infect humans.

Many roundworms are parasites of plants or animals and are responsible for several widespread human diseases.

Earthworms are annelids that play an important role in recycling dead plant material.

11.8 Most mollusks live in shells. 11.8 Most mollusks live in shells.

GastropodsGastropods

Snails and slugs are called gastropod mollusks.

“Belly foot”

Found in both aquatic and terrestrial environments, snails and slugs account for three-quarters of all mollusks.

Bivalve Mollusks

Clams, scallops, oysters, and mussels have a pair of shells that clamp together.

Roughly 8,000 species of bivalves—most of them live in the ocean.

All are filter feeders.

CephalopodsCephalopods


Mollusks are protostome invertebrates that do not molt.

They are the second most diverse phylum of animals and include snails and slugs, clams and oysters, and squids and octopuses.


Most mollusks have a shell for protection, a mantle of tissue that wraps around their body, and a specialized tongue called a radula.

11.1011.10 An external skeleton and An external skeleton and metamorphosis produced the metamorphosis produced the

greatest adaptive radiation ever.greatest adaptive radiation ever.

Mammals get bigger and Mammals get bigger and bigger the more they eat. bigger the more they eat.

Why don’t insects?


The arthropods are protostome invertebrates, and with nearly one million species (and probably at least as many more yet to be identified), they outnumber all other forms of life in species diversity.


The ability to fly and the development of a body with a rugged exoskeleton have contributed to the enormous ecological diversity of insects.

The life cycle of most insects includes a larval stage that is devoted to feeding and growth, a pupal stage during which metamorphosis occurs, and an adult stage in which the insect reproduces.

11.11 Other arthropods include 11.11 Other arthropods include arachnids, crustaceans, millipedes, arachnids, crustaceans, millipedes,

and centipedes. and centipedes.

Millipedes and Centipedes Millipedes and Centipedes

• “A thousand feet” and “a hundred feet”

• Long, segmented bodies

• Millipedes feed on decaying plant material.

• Centipedes are predators; they use venomous fangs to kill insects and even small mammals.

ArachnidsArachnids

Land-dwelling arthropods

Include spiders, scorpions, mites, and ticks

Usually have four pairs of walking legs • And a specialized feeding apparatus

Only have legs on the thorax

Spider VenomSpider Venom

Arachnids are predators

Black widow spider

Brown recluse spider

The CrustaceansThe Crustaceans

• Lobsters, crayfish, crabs, and shrimps

• All have five pairs of appendages extending from their heads.

• Many pairs of legs modified for many purposes

• Most are aquatic.


Centipedes are predators with fangs that inject venom, and millipedes are herbivores that feed on dead plant material.

Spiders and scorpions are predatory arthropods that eat insects and, occasionally, small vertebrates.

Lobsters, crabs, shrimp, and barnacles are predatory marine crustaceans.

11.12 Echinoderms are 11.12 Echinoderms are vertebrates' closest invertebrate vertebrates' closest invertebrate

relativesrelatives

And include sea stars, sea urchins, and sand dollars

Evolutionary SpecializationEvolutionary Specialization

Radial symmetry in adults

An evolutionary specialization associated with their locomotor mode and feeding specializations

Echinoderms and ChordatesEchinoderms and Chordates

Bilateral symmetry in larvae

The larvae have anatomical characteristics in common with the larvae of primitive chordates.

Echinoderms and chordates are each other’s closest relatives.


Because they are deuterostomes (as are vertebrates), echinoderms are the invertebrates that are the closest evolutionary relatives to the vertebrates (and other chordates).

Their aquatic larvae are bilaterally symmetrical and share some anatomical features with chordates, but adult echinoderms are radially symmetrical.

biol 108 chp 11-pt 1: animal diversification

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