Animal Diversity II - Lecture 3

First Split in Animal Evolution History

Tissues vs. Non-Tissues

Porifera: no tissues

Cnidarians and the rest: tissues

Bilateral Symmetry

Symmetry where you can only make one cut and have equal sides, including:

• Dorsal-Ventral (top-bottom)

• Anterior-Posterior)

Cephalization

The development of much sensory equipment concentrated in the anterior head (head development)

Cephalization of Radial Symmetry vs. Bilateral Symmetry

Radial: Nerves are scattered everywhere (sessile or weakly swimming)

Bilateral: clusters of neurons concentrated in certain regions, formation of head (ganglia / brains) (active movement)

Gut evolution: Bilaterial vs. Cnidarians

Cnidarians: gastrovascular cavity, only one hole for the mouth and one for the anus

Complete gut: Derived character of the rest of the animals

Difference in Blastospore fate in Protostomes and Deuterostomes

Protostomes: The mouth develops first, the anus may form later (ex: Snails)

Deuterostomes: The anus develops first, then the mouth forms later (ex: Chordates)

3 Clades of Bilateria

• Deuterostomia

• Lophotrochozoa

• Ecdysozoa

3 Clades of Deuterostomia

• Hemichordata

• Echinodermata

• Chordata

Hemichord, Chord, Echinoderm

Echinodermata Structure (Starfish)

• Water vascular System + Ampulla (movement)

• Tube Feet → locomotion/sensing

Echinoderm Symmetry throughout the life cycle

Larva: bilateral symmetry

Adult: Pentaradial symmetry (starfish!)

3 Clades of Echinodermata

• Asteroidea

• Echinoidea

• Holothuroidea

Aster, Echin, Holothur + Oidea >:)

Exemplify how Segmentation is from Covergent evolution

• 3 Major Phyla, not very related have them:

• Annelida, Arthropoda, Chordata

3 Clades of Chordata

• Cephalochordata

• Urchochordata

• Vertebrata

Cephelo, Uro, Vertebrates >:)

Notochord

Cartilage Structure of Chordates:

• Structural Support and strength

Dorsal Hollow Nerve Cord

A development of the central nervous system that will grow to the spinal cord

• sits atop the notochord

Muscular Segementation

A trait of Chordata, seen in us humans and fish

Pharyngeal Gills/Slits

A characteristic of chordates that:

• Allow for movement for water

• Suspension feeding

Post-Anal Tail

A feature among Chordates that can be reduced during embryotic development (ex: Humans)

• Contains skeletal elements and muscles

Cephalochordata Structure (Lancelets)

Keeps the essential features of a chordate through its whole life cycle:

• dorsal hollow nerve cord

• notochord

• Pharyngeal slits

• muscle segmentation

• post-anal tail

The most basal group of all the chordates

Urochordata Structure (Tunicates)

Larva: have chordate characteristics:

• Notochord

• Dorsal hollow nerve cord

• Muscle Segmentation

• Pharyngeal slits

• Post-anal tail

Adult (metamorphosis): Lose them (except pharyngeal slits)

Urochordata Feeding Mechanism

• Captures food through cilia, letting in water + the nutrients it may carry

• Lets out food through an excurrent siphon

Vertebrate Diversity vs. Animal Diversity

Animals: VERY diverse: many bugs, invertebrates, worms

Vertebrates: small piece of the pie, way less diverse despite our bias to classify them more

Chordata Structure

• Vertebrate enclosed spinal cord

• Elaborate Skull

• (In aquatic Forms) Fin rays

2 Reasons why the Skeletal + Nervous system are evolutionary advantages

Helps with

• Capturing Food

• Evading Predators

First Organisms to be vertebrates

• Hagfish (bottom ocean scavengers)

• Lampreys (parasites)

Both with cartilage skulls and jawless mouths

Outlined Jaw Evolution

Jaws grew from the Pharyngeal Slits, moving forward as to modify the facial structure

Gnathostoma

A Clade of Jawed Vertebrates, including:

• Sharks

• Reptiles and Birds

• Mammals (us!) (we are considered jawed fish in this clade)

Osteichthyes/Osteichithyan Clade Structure

Fish that comprise of a skeletal structure, divided into two subcategories

Ray-Finned Fish

Subcategory of Osteichthyes/Osteichithyan Clade

• Flexible rays modified for maneuvering + defense

• Trout/Salmon/Cod

Lobe-Finned fish

A subcategory of the Osteichthyes/Osteichithyan Clade

• Their fins have muscles

• From which tetrapods and limbs developed

Tetrapod Structure

• Limbs (from fins)

• Head separated from the body by a neck

• Pelvis bones fused to backbone

• Adults, no gills (except Salamanders)

Amphibian Exceptions to the Tetrapod Structure

Salamanders:

• Still have gills as adults (some land, some water)

Frogs:

• Larva stage still has gills

- Both: External Fertilization

Amniota

All tetrapods, excluding the amphibians

Amnion Derived Character (list all 4 + Functions)

An egg with four membranous sacks

• Amnion: Shock absorber

• Chorion: Gas exchange

• Yolk Sac: Nutrients

• Allantois: Waste Storage

Advantages of Amnion egg development

• Eggs can be laid

• No longer requires water (Amphibian eggs need more concentrated O2 diffusion, best in water)

Mammalia

A clade of animals characterized by their nourishment with milk and hair

3 Clades of Mammalia

• Monotremata

• Marsupials

• Eutherials

Monotremata: How they are Unique Mammals

They still lay eggs

• ex: Platypus :D

Marsupial vs. Eutheria Gestation

Gestation: time it takes for organism to develop from an embryo to an adult

Marsupial: VERYYYYY long

Eutherial: Shorter (Humans!)

Lophophore

A feeding structure among lophotrochozoans

• Ectoprocta

• Brachiopoda

Trochophore Larva

A particular larva form unique to certain lophotrochozoans

• Annelids

Characteristics of Lophotrochozoan Ancestor (does not mean all descendants have these)

• Coelem

• Digestive Track, Two Openings

Mollusca structure

Lophotrochozoan Structure with:

• Muscular Foot (movement)

• Mantle (cover, shell, water-filled chamber)

• Radula

• Visceral Mass (internal organs)

Radula

A tongue that takes food off a substrate [covered in microscopic teeth]

4 Clades of Molluska

• Gastropods

• Bivalves

• Polyplacophora

• Cephalopoda

Gastropod Structure

• Shell is one big piece (snails)

• Radula are used to feed on plants and algae

Bivalvia Structure (how it differs from brachiopoda)

• Two piece shell (Left and Right shells, opposed to top/bottom shells)

• No distinct Head

• Sedentary + Suspension Feeders

Polyplacophora structure

Organisms named Chitons have:

• Many pieces of shell

• Scrapes of algae from rocks

Cephalopoda structure

• Tentacles to grasp prey

• Lost or very small shell

Cephalopoda Evolutionary Advantages

• Intelligence

• Camouflage

• Highly developed sensory shit

Annelida Structure + Development

• Segmentation

• Compartmentalized organs

• Trochophore Larva Stage and Metamorphisis

2 Clades of Annelida

• Errantia

• Sedentaria

Errantia Characteristics

• Segmentation, like all annelids

• Mobile predators / Grazers (Marine)

• Appendages, Parapodia Sticking out for locomotion

Sedentaria Characteristics

• Move less

• Elaborate Gills

Leeches

Sedentary organisms that can be predators, feeding on other vertebrates

Earthworms

Sendetaria that extract nutrients from the soil!

Brachiopoda Structure

• Has a lophophore, but no trochophore larvae

• Two muscles: one opens, one closes

Brachiopoda Symmetry

• Two halves are dorsal and ventral rather than lateral like Bivalves

2 Clades of Brachiopoda

• Inarticulata

• Articulata

Inarticulata Structure

• Small or no hinge (Lingula)

• Complete gut: mouth + intestinal track + anus

Articulata Structure + Digestion

• large hinge

• incomplete gut, no real place for waste → come in through mouth, processed, leaved through mouth

• Intestine protrudes out of the back of the shell

Platyhelminthes Structure (Flatworms)

• Light-sensative Eye Spots

• Gastrovascular Cavity

• Acoelomates

• Gas Exchange through skin, very close b/c high SA:V

3 Clades of Platyhelminthes

• Turbellarian

• Trematoda

• Cestoda

Neodermata + Subgroup Structure

Clade of Platyhelminthes comprising of the trematodes and cestodes

• trematodes: Schistosoma, parasitic worm

• Cestodes: tapeworms, no gastrovascular cavity!

Ecdysozoa Unique Structure

Exoskeleton, a cuticle/shell that periodically sheds and reforms (Ecdysis)

2 Phylums of Ecdysozoa

• Nematoda

• Anthropods

Nematoda Structure (Roundworms)

• Psuedocoelomate body structure

• Body covered with flexible cuticle + periodic sheds

The MOST COMMON animal on Earth!!

• Either parasitic (needs host) or free-living (no need for host)

Important Model Organism in Research + Why: A Nematode

Caeonohabditis Elegans

• known genome

• Small size

• easy to grow

• simple body, lots known!

Arthropod Structure

• Segmented Body

• Hard exoskeleton, completely covered in cuticle

• Jointed appendages

• Tagmata (segments grouped together)

• Open circulatory system

Open vs. Closed Circulatory System

Function of Appendages

• walking (legs)

• defense (claws, intimidation)

• fangs (spiders, inject venom)

• sensation (antenna)

3 Clades of Arthropods

• Chelicerata

• Myriapoda

• Pancrustacea

Chelicerata 2 Clades

• Eurypterids

• Arachnids

Chelicerata Structure

• 6 pairs of appendages (1 Chelicerae, 1 Pedipalps, 4 pairs of legs)

• Sensitive eyes

• Open circulatory System

2 Arachnid Tagmata Structure

• Posterior Abdomen: Heart/Reproductive Structures/Digestive System/Poison and Silk glands

• Cephalothorax

Myriapoda: Centipede vs. Millipede difference

Centi: one pair of legs, carnivorous

Milli: two pairs of legs, herbivorous

Pancrustacea Evolutionary History

• Insects are more related to crustaceans than myriapods

• Some crustaceans are still excluded, hence the group is paraphyletic

Chelipeds

Claw-like appendages that characterize crustacea (lobsters)

Crustacea Structure

Two segment groupings (tagmata)

• Sephalothorax: manner antennae, chelipeds, and walking legs

• Abdomen/tail: much muscle

Hexapoda Structure (Anthropod clade)

• insects and 6-legged kin

• Do complete or incomplete metamorphosis

• Lightweight exoskeleton of Chitin

• Head - 5 Segments

• Thorax - 3 Segments

• Abdomen - up to 11 Segments

Incomplete vs. Complete metamorphosis

Complete: Larva to adult

Incomplete: Young nymphs already ressemble adults, true bugs do this

Structure of ALL Insects

• 3 Body parts

• 6 Legs

(usually, they have 4 wings and 2 antennae)

How flight Evolved in Insects

• Hexopoda clade

• Wings were an extension of the exoskeleton and cuticle, NOT APPENDAGES

• Evo. adv: escape predators, find food, find new habitats faster

4 Clades of Hexapoda that do Complete Metamorphosis

1. Beetles

2. Flies

3. Wasps and Bees

4. Moths

2 Claes of Hexapoda that do Incomplete Metamorphosis

1. True Bugs

2. Grasshoppers