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Arthropods, Echinoderms, and Chordates

Bi 10 10/22/2013

Revised Schedule • Friday, Nov. 22: Chapter 17, Part 2

• Chapter 15, 16 Reading Quiz Due

• Wednesday, Nov. 27: Special Lecture: Review + World’s Weirdest Fungi (NO LAB)

• ESSAY 3 Outline Due

• Chapter 17 Reading Quiz Due

• December 4: Chapter 18, LAB PRACTICAL

• December 6: Chapter 21, LAB PRACTICAL

• Chapter 18, 21 Reading Quiz Due,

• December 13: Lecture Final Exam, Essay 3 Due, Last Study Guides Due, Extra Credit Museum Trip Due

Take a Wild Guess

About how many insects are there for every single person on earth? That is to say, by what factor do insects outnumber us?

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Adaptations of Animal Phyla • Specialized cells for eating

• Organized tissues

• Bilateral symmetry

• True coelom (body cavity)

• Segmentation

• Notochord/spine

Tissue Layers

Most animals have three layers of tissue.

Ecto = outer. Ectoderm = outer skin. Makes the skin

and nerves.

Meso = middle. Mesoderm makes the muscles.

Endo = inside. Endoderm makes the gut.

Pocket lined by mesoderm is called a coelom.

Arthropods: Segmented Invertebrates with Jointed Exoskeletons

Arthropods are the most successful animal group on Earth. Most animals are arthropods!

They have a hard, jointed shell called an exoskeleton.

What are some advantages and disadvantages of having an exoskeleton with specialized segments?

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Arthropods: Millipedes and Centipedes Millipedes are among the earliest land animals, and used to grow up to a meter long! Scavengers, vegetarians.

“Diplopods” – two pairs of legs per segment.

Centipedes are predators. The front legs are modified into venomous fangs. Contrary to the text, some can

deliver a painful bite.

Arthropods: Class Arachnida Four pairs of legs (1), plus special claws/“feelers” for grasping food.

Two segments: thorax/head fused (2) and abdomen (3).

Mouthparts

How can you tell an arachnid apart from an insect?

Arthropods: Subphylum Crustacea Have 3+ pairs of legs and a larva that usually looks different from the adult. Close relatives of insects!

Fiddler crab larvae Fiddler crab adult

Note specialized feeding mouthparts and legs.

Isopod (“same legs”)

Copepod (tiny crustacean)

Krill (also tiny) Lobster

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Arthropods: Class Insecta Have 3 pairs of legs – no more, no fewer. 3 segments: head, thorax, abdomen.

Most successful group of animals on Earth!

Insect Diversity

A small sample of the diversity of insects on earth:

Beetles cover their soft inner wings with hard outer wings.

Bugs suck up their food, and tend to have crossed wings.

Ants and wasps have two pairs of gauzy wings

Insects play many critical roles, including decomposition, pollination of flowering plants, predation, and being a food

source for other animals!

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Adaptations of Animal Phyla • Specialized cells for eating

• Organized tissues

• Bilateral symmetry

• True coelom (body cavity)

• Segmentation

• Notochord/spine

Phylum Echinodermata “Echinoderm” means “spiny-skinned.” Aquatic animals with near-radial symmetry as adults and bilateral

symmetry as larvae.

Vascular system uses water, not blood!

Like us, they have an endoskeleton (skeleton inside).

Phylum Chordata This is our phylum! It includes the vertebrates, animals with backbones.

The backbone develops from a simpler structure called a notochord. The notochord comes from mesoderm, and

helps protect the spinal cord.

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Echinoderms and Chordates vs. Other Animals

In most animals the hole made when the blastula

folds in becomes the mouth.

In both echinoderms and chordates, the hole made

when the blastula folds in becomes the anus.

This is one of the clues that echinoderms are our

sister phylum (cousins)!

Chordate Subphyla

Not all chordates have vertebrae, or even bones!

Tunicates Lancelets

Vertebrates

Chordate Adaptations

Different classes of chordates evolved many adaptations to life on land.

Jaws and backbone

Tetrapod (four-footed)

limbs

Amniotic sac (in egg or inside

mother)

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Cartilaginous vs. Bony Fish

Know that sharks have cartilaginous skeletons, while ray-finned fish have bony skeletons!

Icthyos = fish. Class Chondryichthyes = cartilaginous fish, like sharks.

Osteichthyes = bony fish. Includes ray-finned fish

Fish are the most successful vertebrates on earth in terms of species count.

Class: Amphibia First tetrapods. Legs evolved from lobed fins of fish.

Need to live near water; lay eggs in water and breathe through lungs and skin.

Class: Reptilia Evolved amniote egg, which can be laid on land without drying out. (Mammals are also amniotes.)

Reptiles, like amphibians, are ectotherms – except for birds, which are endotherms!

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Class: Mammalia Give birth to live young (except for monotremes), have hair, lactate milk. (Monotremes secrete it from fur, not

nipples.)

Marsupial mammals (~5% of mammals) give birth to poorly developed young and keep them in a pouch.

Placental mammals have longer pregnancies and no pouch.

Class Mammalia, Order Primates

Review: Chordate Adaptations

Different classes of chordates evolved many adaptations to life on land.

Jaws and backbone

Tetrapod (four-footed)

limbs

Amniotic sac (in egg or inside

mother)