Animal Diversity and the Evolution of Body Plants

All animals are _____ (in terms of what they eat)

Heterotrophs

What is the exception to the heterotrophs rule?

Sea slugs can sometimes harvest chloroplasts from other organisms

What do animals lack and have in terms of cell structure?

Lack cell walls have an ECM

True or False: Most animals can actively move

True

Animals are diverse in what two aspects?

Form and habitat

What is the phylum that is only fully terrestrial?

Phylum Onychophora (ex: velvet worms)

True or False: Most animals don’t have characteristic embryonic development

False

Step 1 of Embryonic Development

Haploid cells meet to form a zygote (2n)

Step 2 of Embryonic Development

Zygote undergoes cleavage to get to the 8 cell stage

Step 3 of Embryonic Development

8 cell stage undergoes cleavage again to form the blastula

Cleavage

Rapid cell division to form a multicellular structure

Blastula

Hollow ball of several cells

Blastocoel

fluid filled cavity that makes up the inside portion of the blastula

Step 4 of Embryonic Development

Gastrulation occurs

Gastrulation

• evagination of tissues

• Blastula folds into a 3 layered gastrula

What are the layers of the gastrula from inside to out?

• Blastopore

• Archenteron

• Endoderm

• Mesoderm

• Blastocoel

• Ectoderm

All or most: Blastula (cleavage stages)

all animals have this

All or most: Gastrula

Most animals have this

All or most: Larva

Most animals

What is an important animal characteristic in terms of orgnaization?

Cells are organized into tissues (except sponges). Muscle and neuronal tissues are unique to animals.

What are the 5 key innovations noted in animal evolution?

1. Symmetry

2. Tissues

3. Body cavity

4. Various patterns of embryonic development

5. segmentation

Animals exhibit ______ or ______ symmetry (except sponges ofc)

radial, bilateral

Radial Symmetry

Body parts are arranged around a central axis

Can be bisected through the central axis into 2 equal halves

Types of animals that have radial symmetry

Cnidaria, Echinodermata
Starfishes, sea urchins, sea anemone, hydra

What’s special about the adults vs the larvae of starfishes and sea urchins?

The adults have radial symmetry but the larvae have bilateral symmetry

Bilateral Symmetry

• most animals = bilateria

• body has right and left halves that are mirror images

• splitting doesn’t include internal organs, just the outside

What plane bisects the animal into 2 equal halves in bilateral symmetry?

The sagittal plane

Dorsal

On the upper side or back of an animal

Ventral

On the underside or abdominal area of an animal (belly)

Posterior

Near the rear or hind end of an animal

Anterior

Near the front or head of the animal

Frontal Plane

Vertical plane that divides the animal into anterior and posterior sections

Transverse Plane

Horizontal plane that divides the body in to a superior (top) and inferior (bottom) halves

Sagittal Plane

Vertical plane that divides the body into the right and left sides

What are the two main advantages of bilateral symmetry over radial symmetry?

greater mobility and anterior cephalization

Animals with bilateral symmetry can move….

Through the environment in a consistent direction

Anterior cephalization

the animal body becomes more specialized and streamline which creates the evolution of a definite brain and nervous system area

What are the advantages of having radial symmetry compared to bilateral symmetry?

can move in any direction (but its slow) and whole body can respond to stimuli

Why in radially symmetric animals can the whole body respond to one stimuli?

Due to a decentralized nervous system

What are the two phylum names that are exceptions to the bilateral symmetry tule?

Porifera and Cnidaria

What phylum has no symmetry?

Placozoa

What did the evolution of tissues allow for?

Specialized structures and functions

Differentiation during the embryonic phase allows for what?

specialization of cells and organ formation

In animals, differentiation is _____ except in _____

irreversible, sponges (duh)

Why is differentiation irreversible in sponges and some plant species?

because they can switch between undifferentiated and differentiated cells

Stem cells are….

undifferentiated but they can differentiate

The rarity of animals with the ability to dedifferentiate cells suggests what?

that cell specialization carries an evolutionary advantage

What is the breakdown of the differentiation of the endoderm cells?

endoderm → pancreas → gut, alpha, beta and other cells associated with the gut

Body Cavity

A hollow space that is formed during development and is surrounded by MESODERM tissue :))))

Having body cavities made possible the development of what?

advanced organ systems

How many germ layers do the embryos of Bilateria produce?

3  (triploblastic)

The ectoderm, mesoderm, and endoderm only exist where?

In the embryo

What does the outer ectoderm specialize into?

the skin and nervous system

What does the mesoderm specialize into?

most stuff

bones, skeletal and cardiac muscle, blood and vasculature, urogenital system, arteries, veins, cartilage, etc.

What does the inner endoderm specialize into?

digestive organs, digestive tract, intestines, stomach, pancreas, liver, etc

Cnidarians and some ctenophores are ______ and lack ______

diploblastic, organs

What animal has no germ layers?

sponges

What is the mesoderm/body cavity filled with?

liquid (in most animals) and gas (humans)

How does liquid work in the mesoderm?

Muscles squeeze on the fluids to help distribute food, wastes, and hormones from one part of the animal to the other

How does gas work in the mesoderm?

Humans and some other animals have tension in their muscles and tendons that helps move the gas and other materials around the body

Hydrostatic Skeleton

a support system in many soft-bodied organisms that uses a fluid-filled cavity (pressure) to provide structural support and facilitate movement

Acoelomates

• no body cavity

• no internal cavity that is sealed off from the external environment

• ex: flatworms (planarea)

Pseudocoelomates

• contains the pseudocoel

• true body cavity

• round circle sealed off from external environment

• ex: roundworms, nematodes

pseudocoel

body cavity between the mesoderm and endoderm

Coelomates

• have coelom

• paratheses shaped hollow inside sealed off from external environment

• ex: annelid

Coelom

• “hollow”

• body cavity entirely in the mesoderm

What are the two types of deuterostomes?

Echlinodermata and Chordata

Most invertebrates are…

protostomes

The evolution of the coelom is most likely…

a result of convergent evolution which disproves the idea that you can track ancestry based on coelom

Coeloms evolved ____ in an ancestor of _____ and _____

once, protostomes, deuterostomes

True or False: all deuterostomes have a coelom

true

stome

mouth

What are the 2 main types of development for Bilaterians?

protostome and deuterostome

The blastula indents to form a 2 layer thick ball with what 2 things?

blastopore (opening to outside) and archenteron (primitive body cavity)

Protostome

• mouth first

• most bilateria

• develop the mouth first from or near the blastopore

• anus develops later, either from blastopore or another region

Deuterostome

• mouth second

• Echinoderms (sea stars) and chordates (vertebrates)

• develop anus first from blastopore

• mouth develops later from another region 

What did segmentation allow for?

redundant systems and improved locomotion

Segmentation

• linear array of compartments that look alike, at least in the embryo

• underlies the body organization of many morphologically complex animals

somite

a segment of the segmented portion

What are the 2 advantages segmentation provides?

1. allows redundant organ systems in adults (like annelids)

2. allows for more efficient and flexible movement

Why are redundant organ systems an advantage?

1. if segment is damaged, they can still survive and grow

2. segments can become specialized

Why does segmentation allow for more efficient movement?

because each segment can move semi independently

Metazoans are traditionally divided into how many phyla?

35-40

What is the main goal of phylogeny?

to determine evolutionary history

Systematic Classification

uses characteristics (molecular or morphological) that are assumed to have evolved only once

What type of characteristic do animals have to share to be more closely related?

a molecular or morphological trait that has been assumed to evolve only once

King Philip Cried Out For Good Soup

Kingdom, Phylum, Class, Order, Family, Genus, Species

Morphology and molecule based phylogenies primarily agree on what?

major animal groupings

What does it mean when all animals are monophyletic?

They all descended from a common evolutionary ancestor

What 2 factors separate Parazoa and Eumetazoa?

tissues and symmetry

Parazoa lack…

symmetry and tissues (sponges0

Eumetazoa have…

good symmetry and tissues

What are some important characteristics of Eumetazoa (diploblastic)?

radial symmetry

What are some important characteristics of Eumetazoa (triploblastic)?

• bilateral symmetry 

• coelom type

• type of development

Molting

shedding skin or exoskeleton

Ecdyxozoa = molting animals

What 2 animals were thought to be closely related and because of what factor?

Annelids and Arthropods were thought to be closely related because of characteristic segmentation but molecular data showed that segmentation arose more than once during evolution

Ecdysozoa

• molting animals

• grow in a step wise manner

• molting evolved once

• ex: nematodes (roundworms), arthropods (sea creatures, insects), and tardigrades

What are the 2 major phyla for lophotrochozoa?

mollusks and annelids

What are the characteristics of lophotrochozoa

• grow by gradual addition of body mass (aka not molting)

• spiral cleavage

• trochophore larvae

• lophophore feeding apparatus (bryozoa and brachiopods)

Spiral Cleavage

As the embryo continues to divide in cells, the base for which the cells rest on keeps shifting (aka the plane shifts)