Chapter 32 Introduction to Animal Diversity...The oldest fossils (bacteria) are between 3 billion and 3.5 billion years old. More complex animals appeared in the oceans about 565 million

Chapter 32

Introduction to Animal Diversity

Review: Biology 101

There are 3 domains: They are…

Archaea

Bacteria

Eukarya

Protista!

Endosymbiosis (proposed by Lynn Margulis)

is a relationship between two species in which one

organism lives inside the cell or cells of the other

organism (the host)

This is the root of the diversity of life.

http://evolution.berkeley.edu/evolibrary/article/_0_0/endosymbiosis_04

Mitochondria and plastids are derived from

prokaryotes that were engulfed by the ancestors of

early eukaryotic cells

Mitochondria evolved once by endosymbiosis of an

alpha proteobacterium

The ancestral host cell may have been an archaean

or a “protoeukaryote,” from a lineage related to, but

diverged from archaeal ancestors

What makes a Kingdom?

A Kingdom is a division of life,

right under Domain.

Boundless. “The Levels of Classification.” Boundless

Biology. Boundless, 03 Jul. 2014. Retrieved 12 Dec. 2014

from https://www.boundless.com/biology/textbooks/boundl

ess-biology-textbook/phylogenies-and-the-history-of-life-

20/organizing-life-on-earth-133/the-levels-of-classification-

541-11750//

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Welcome to Your Kingdom

The animal kingdom extends far beyond humans

and other animals we may encounter

1.3 million living species of animals have been

identified

Fig. 32-1


• Animals are heterotrophs that ingest their

food

http://www.reefs.org/library/aquarium_net/0697/0697_1.html

http://greenanswers.com/q/183382/animals-wildlife/which-animal-

eats-most-food-every-day

Animal characteristics


What makes an Animal?

• Animals are multicellular

eukaryotes

• Heterotrophs that digest internally

• Their cells lack cell walls

• Their bodies are held together by

structural proteins such as collagen

• Nervous tissue and muscle tissue

are unique to animals


Reproduction and Development

• Most animals reproduce sexually, with the

diploid stage usually dominating the life cycle

• After a sperm fertilizes an egg, the zygote

undergoes rapid cell division called cleavage

• Cleavage leads to formation of a blastula

• The blastula undergoes gastrulation, forming

a gastrula with different layers of embryonic

tissues

The Earth is about 4.5 billion (4,500,000,000)

years old. The geological time scale divides up

this vast time interval.

The Earth is very old


The history of animals spans more than half a billion years

The animal kingdom

includes a great diversity

of living species and an

even greater diversity of

extinct ones

The common ancestor of

living animals may have

lived between 675 and

875 million years ago

This ancestor may have

resembled modern

choanoflagellates,

protists that are the closest

living relatives of animals

The oldest fossils (bacteria) are between 3 billion and

3.5 billion years old.

More complex animals appeared in the oceans about

565 million years ago, and became much more common

about 542 million years ago. This is the start of a division

of geological time called the Phanerozoic Eon.

Phanerozoic means "visible life", and is the time in which

fossils are abundant. http://commonfossilsofoklahoma.snomnh.ou.edu/geological-time-scale


Neoproterozoic Era (1 Billion–524 Million Years Ago)

Early members of the animal fossil record include

the Ediacaran biota, (pre-Cambrian) which dates

from 565 to 550 million years ago

• All life was soft-bodied

Mawsonites spriggi

Spriggina floundersi


Paleozoic Era (542–251 Million Years Ago)

The Cambrian explosion (535 to 525 million years

ago) marks the earliest fossil appearance of many

major groups of living animals

Several hypotheses

regarding the explosion

1. New predator-prey

relationships

2. A rise in atmospheric

oxygen

3. The evolution of the

Hox gene complex

http://geologycafe.com/class/chapter13.html

Fig. 32-5

Animal diversity continued to

increase through the Paleozoic, but

was punctuated by mass extinctions

Animals began to make an impact

on land by 460 million years ago

Vertebrates made the transition to

land around 360 million years ago


Mesozoic Era (251–65.5 Million Years Ago)

• Coral reefs emerged, becoming important

marine ecological niches for other organisms

• During the Mesozoic era, dinosaurs were the

dominant terrestrial vertebrates

• The first mammals emerged

http://www.smithsonianmag.com/smart-news/dinosaurs-have-feathers-sure-

but-we-may-have-got-the-colors-all-wrong-10978826/?no-ist

Cenozoic Era (65.5 Million Years Ago to the

Present)

The beginning of the Cenozoic era followed mass

extinctions of both terrestrial and marine animals

These extinctions included the large, nonflying

dinosaurs and the marine reptiles

Modern mammal orders and insects diversified during

the Cenozoic


Animals can be characterized by “body plans”

A body plan is a set of morphological and

developmental traits – we will classify animals

by:

1. Symmetry

2. Tissues

3. Type of body Cavity

4. Fate of the blastopore


• Hox regulates the development

of body form

• Lay out the basic body form of

all animals

• it doesn’t matter if it’s a mouse’s

head or a fly’s head that is

being built, the same gene

directs the process

• Jellyfish have only two Hox

genes, bilateria have at least

seven.

All animals, and only animals, have Hox (Homeobox)

genes


• Many animals have at least one larval stage

• A larva is sexually immature and

morphologically distinct from the adult; it

eventually undergoes metamorphosis

Metamorphosis - Some animals change body

plans during their life-cycle

1. Symmetry

Animals can be categorized according to the

symmetry of their bodies, or lack of it

Sponges are asymmetrical – they have asymmetry

http://encina.pntic.mec.es/~nmeb0000/invertebrates/ranimal.html

http://biologismos.blogspot.com/2010_06_01_archive.html


• Animals can be categorized according to the

symmetry of their bodies, or lack of it

• Some animals have radial symmetry

(a) Radial symmetry Fig. 32-7

1. Symmetry


(b) Bilateral symmetry

Fig. 32-7

Bilaterally symmetrical animals have:

– A dorsal (top) side and a ventral (bottom) side

– A right and left side

– Anterior (head) and posterior (tail) ends

– Cephalization, the development of a head

1. Symmetry


2. Tissues

• Tissues are collections of specialized cells

isolated from other tissues by membranous

layers

• During development germ layers give rise to

the tissues and organs of the animal embryo


• Ectoderm is the germ layer covering the

embryo’s surface

• Endoderm is the innermost germ layer and

lines the developing digestive tube.

• Diploblastic animals have ectoderm and

endoderm

• Triploblastic animals also have an intervening

mesoderm layer; these include all bilaterians

2. Tissues


3. Body Cavities

• Most triploblastic animals possess a body

cavity

• A true body cavity is called a coelom and is

derived from mesoderm

http://en.wikipedia.org/wiki/File:Scheme_body_cavities-en.svg

3. Body Cavities

Animals that are Diploblastic (like jellyfish) or do

not form a blastula (like sponges) have no body

cavity. We say that they have No Coelom


• Triploblastic animals that lack a body cavity are

called acoelomates

(c) Acoelomate

Body covering

(from ectoderm)

Wall of digestive cavity (from endoderm)

Tissue- filled region

(from mesoderm)

3. Body Cavities


• A pseudocoelom is a body cavity derived from

the mesoderm and endoderm

• Triploblastic animals that possess a

pseudocoelom are called pseudocoelomates

Pseudocoelom

Body covering

(from ectoderm)

Muscle layer (from mesoderm)

Digestive tract

(from endoderm)

(b) Pseudocoelomate

3. Body Cavities

Fig. 32-8a

Coelom Body covering

(from ectoderm)

Digestive tract

(from endoderm)

Tissue layer lining coelom and suspending internal organs (from mesoderm)

(a) Coelomate

Coelomates are animals that possess a true coelom

3. Body Cavities


4. Protostome and Deuterostome Development

• Based on early development, many animals

can be categorized as having protostome

development or deuterostome development

Zygote

Cleavage

Eight-cell stage

Cleavage Blastula

Cross section of blastula

Blastocoel

Gastrulation

Blastopore

Gastrula

Archenteron

Ectoderm

Endoderm

Blastocoel


• The blastopore forms during gastrulation

• Protostome:blastopore becomes the mouth

• Deuterostome: the blastopore becomes the anus

Anus

Protostome development

(examples: molluscs,

annelids)

Deuterostome development

(examples: echinoderms,

chordates)

Anus

Mouth

Mouth

Digestive tube

(c) Fate of the blastopore

Key

Ectoderm

Mesoderm

Endoderm

Mouth develops from blastopore. Anus develops from blastopore. Fig. 32-9c



• Protostome: the splitting of solid masses of

mesoderm forms the coelom

• Deuterostome: the mesoderm buds from the wall

of the archenteron to form the coelom

Coelom

Protostome development

(examples: molluscs,

annelids)

Deuterostome development

(examples: echinoderms,

chordates)

(b) Coelom formation

Key

Ectoderm

Mesoderm

Endoderm

Mesoderm Mesoderm

Coelom

Archenteron

Blastopore Blastopore

Solid masses of mesoderm

split and form coelom. Folds of archenteron

form coelom.

Fig. 32-9b


Figure 32.11

ANCESTRAL

PROTIST

Porifera

Ctenophora

Cnidaria

Acoela 770 million

years ago

680 million

years ago

670 million

years ago

Me

tazo

a

Eu

me

tazo

a

Bila

teria

Hemichordata

Echinodermata

Chordata

Platyhelminthes

Rotifera

Ectoprocta

Brachiopoda

Mollusca

Annelida

Nematoda

Arthropoda

De

ute

ros

tom

ia

Lo

ph

otro

ch

ozo

a

Ec

dys

ozo

a

Five important points about the relationships among

living animals are reflected in their phylogeny

1. All animals share a common ancestor

2. Sponges are basal animals

3. True animals Eumetazoa is a clade of animals

with true tissues

4. Most animal phyla belong to the clade

Bilateria

5. Most animals (95%) are invertebrates,

animals that lack a backbone, only some

Chordata, are classified as vertebrates.


You should now be able to:

1. List the characteristics define animals

2. Summarize key events of the Paleozoic, Mesozoic, and Cenozoic eras

3. Distinguish between the following pairs or sets of terms: radial and bilateral symmetry; grade and clade of animal taxa; diploblastic and triploblastic; spiral and radial cleavage; determinate and indeterminate cleavage; acoelomate, pseudocoelomate, and coelomate grades


4. Compare the developmental differences

between protostomes and deuterostomes

5. Compare the alternate relationships of

annelids and arthropods presented by two

different proposed phylogenetic trees

6. Distinguish between ecdysozoans and

lophotrochozoans

Documents

Chapter 32 Introduction to Animal Diversity...The oldest fossils (bacteria) are between 3 billion and 3.5 billion years old. More complex animals appeared in the oceans about 565 million