4.1-4.3 Test 1

Features that Distinguish Kingdom Animalia:

• Multicellular eukaryotes

• Heterotrophic (must ingest food)

• Lack cell walls (unlike plants and fungi)

• Typically possess specialized tissues (except in simpler animals like sponges)

• Capable of sexual reproduction (most), with some asexual methods

• Most have muscle and nerve tissues for movement and responsiveness

• Life cycle includes developmental stages (e.g., embryo formation, sometimes larval stages)

2. Asexual vs. Sexual Reproduction in Animals:

3. Cleavage, Blastulation, Gastrulation:

• Cleavage: Rapid mitotic divisions of the zygote → forms a solid ball of cells (morula).

• Blastulation: Formation of the blastula, a hollow ball of cells with a fluid-filled cavity (blastocoel).

• Gastrulation: Cells migrate inward to form germ layers (ectoderm, mesoderm, endoderm), establishing body axes.

4. Incomplete vs. Complete Metamorphosis:

5. Diploblastic vs. Triploblastic Animals:

6. Fate of Primary Germ Layers (Triploblastic):

• Ectoderm: Skin, nervous system

• Mesoderm: Muscles, bones, circulatory system

• Endoderm: Lining of the gut, liver, pancreas

7. Roles of Hox Genes in Development:

• Regulate the body plan along the head-to-tail axis

• Determine the identity and placement of body parts (e.g., limbs, organs)

• Mutations can lead to misplacement of structures (e.g., legs instead of antennae in flies)

8. Three Types of Body Symmetry:

9. Formation of the Coelom:

• A coelom is a fluid-filled body cavity lined entirely by mesoderm.

• Forms during gastrulation via one of two processes (protostome vs. deuterostome development).

10. Acoelomate, Pseudocoelomate, Eucoelomate:

11. Protostomes vs. Deuterostomes:

12. Earliest Animals – Features & Timeline:

• Soft-bodied, aquatic, filter-feeding organisms (e.g., sponges)

• Lacked hard parts (hard to fossilize)

• Appeared roughly 600 million years ago (late Precambrian era)

13. Cambrian Explosion – Significance:

• Occurred ~540 million years ago

• Marked by a rapid increase in animal diversity

• First appearance of most major animal phyla

• Development of hard parts (exoskeletons, shells) and complex body plans

14. Implications of Mass Animal Extinctions:

• Reshaped biodiversity and opened ecological niches

• Examples:

  • Permian Extinction (~250 mya): 90–95% of species lost

  • Cretaceous Extinction (~66 mya): End of dinosaurs, rise of mammals

• Allowed for adaptive radiations and evolution of new groups

Characteristics of Phylum Porifera (Sponges):

• Asymmetrical, no true tissues or organs

• Sessile (non-motile) as adults

• Filter feeders: water flows through pores into a central cavity and out through the osculum

• Skeleton made of spicules or spongin

• Choanocytes (collar cells) help in feeding and water movement

2. Sexual vs. Asexual Reproduction in Sponges:

3. Characteristics of Phylum Ctenophora (Comb Jellies):

• Radial symmetry

• Diploblastic (2 tissue layers)

• Ciliated comb rows (ctenes) for movement

• Bioluminescent in many species

• Colloblasts (sticky cells) used to capture prey (not stinging cells like cnidarians)

4. Characteristics of Phylum Cnidaria:

• Radial symmetry

• Diploblastic

• Possess cnidocytes (stinging cells) with nematocysts

• Gastrovascular cavity (one opening serves as mouth and anus)

• Nerve net (no centralized brain)

Examples: Jellyfish, corals, sea anemones, hydra

5. Two General Body Forms of Cnidaria:

6. Characteristics of Superphylum Lophotrochozoa:

• Bilateral symmetry

• Triploblastic

• Protostomes

• Many have:

  • Lophophore: Feeding structure (e.g., in brachiopods)

  • Trochophore larvae: Ciliated, free-swimming larvae (e.g., in mollusks and annelids)

7. Key Features of:

• Phylum Platyhelminthes (Flatworms):

  • Acoelomate

  • Bilateral symmetry

  • Incomplete digestive tract (or none in parasitic species)

  • Simple nervous system with cephalization

• Phylum Mollusca:

  • Coelomate

  • Soft body, often with calcium carbonate shell

  • Body plan: head-foot, visceral mass, mantle

  • Most have open circulatory systems (except cephalopods)

• Phylum Annelida:

  • Segmented worms

  • Coelomate

  • Closed circulatory system

  • Well-developed organs and nervous system

8. Unique Features of Mollusks and Annelids:

9. Molluscan Classes & Characteristics:

10. Characteristics of Superphylum Ecdysozoa:

• Bilateral symmetry

• Triploblastic

• Protostomes

• Undergo ecdysis (molting of outer cuticle)

• Includes nematodes and arthropods

11. Characteristics of Phyla:

• Nematoda (Roundworms):

  • Pseudocoelomates

  • Unsegmented, tapered at both ends

  • Complete digestive tract

  • Tough outer cuticle, must molt to grow

  • Many are parasitic (e.g., Ascaris, heartworm)

• Arthropoda:

  • Segmented body (head, thorax, abdomen in many)

  • Exoskeleton made of chitin

  • Jointed appendages

  • Open circulatory system

  • Most diverse animal phylum

12. Subphyla of Arthropoda & Characteristics:

13. Characteristics of Superphylum Deuterostomia:

• Deuterostome development:

  • Radial, indeterminate cleavage

  • Blastopore becomes anus

• Includes phyla Echinodermata and Chordata

• Internal skeletons (in most)

• Coelomates

14. Characteristics of Phylum Echinodermata:

• Radial symmetry as adults (bilateral larvae)

• Water vascular system (for locomotion and feeding)

• Tube feet (part of water vascular system)

• Endoskeleton made of calcareous plates

• No brain, decentralized nerve ring

Examples: Starfish, sea urchins, sea cucumbers, brittle stars

Distinguishing Characteristics of Chordates:

• Notochord: Flexible, supportive rod

• Dorsal hollow nerve cord: Develops into CNS (brain and spinal cord)

• Pharyngeal slits/clefts: Used in feeding, respiration, or develop into other structures

• Post-anal tail: Tail extending beyond anus

• Present at some point in development

2. Characteristics of Invertebrate Chordates:

3. Fate of the Notochord in Vertebrates:

• Replaced by the vertebral column (spine) during development

• Remnants may persist as part of intervertebral discs (nucleus pulposus in humans)

4. Why Hagfish Are Transitional:

• Possess notochord but no vertebrae (some genetic/developmental evidence of rudimentary ones)

• Craniates (have skulls), but lack jaws, paired fins, and vertebral bones → bridge between invertebrates and vertebrates

5. Compare Hagfish vs. Lampreys:

6. Two Major Differences – Jawless vs. Jawed Fishes:

• Jaws: Absent in hagfish/lampreys; present in sharks, rays, bony fish

• Paired fins: Absent in jawless; present in jawed for better mobility and control

7. Cartilaginous vs. Bony Fishes:

8. Ray-Finned vs. Lobe-Finned Fishes:

9. Evolution of Lungs:

• Lungs evolved from outpouchings of the gut, likely for gas exchange in low-oxygen environments

• Present in early lobe-finned fish → led to lungs in tetrapods, and swim bladders in ray-finned fish

10. Tiktaalik – Transitional Fossil:

• Mix of fish and tetrapod features:

  • Fish traits: Scales, fins, gills

  • Tetrapod traits: Neck, flat skull, ribs, limb-like fins with wrist bones

• Important because it shows the evolutionary step between aquatic and terrestrial vertebrates

11. Amphibian Life Cycle vs. Other Vertebrates:

• Dual life: Aquatic larvae with gills → metamorphose into terrestrial adults with lungs

• Other vertebrates (reptiles, mammals, birds) do not undergo aquatic larval stages

12. Main Characteristics of Amniotes:

• Amniotic egg with specialized membranes (amnion, yolk sac, chorion, allantois)

• Adapted for terrestrial life (no need for aquatic larval stage)

• Skin less permeable, more keratinized

• Use of thoracic (rib) breathing

13. Structure of an Amniotic Egg:

14. Anapsids vs. Synapsids vs. Diapsids:

15. Characteristics of Reptiles:

• Scaly, waterproof skin

• Lay amniotic eggs on land

• Ectothermic (except birds)

• Lungs used for respiration throughout life

16. Evolution of Reptiles:

• Evolved from amphibians ~310 MYA

• First amniotes → split into synapsids (mammals) and sauropsids (reptiles and birds)

• Adaptations for dry land: tougher skin, eggs, internal fertilization

17. Major Reptile Groups & Examples:

18. Evolutionary History of Birds:

• Evolved from small theropod dinosaurs (e.g., Velociraptor)

• Archaeopteryx shows transitional features: feathers + dinosaur traits

• Feathers evolved before flight (likely for insulation or display)

19. Flight Adaptations in Birds:

• Feathers: Lightweight and aerodynamic

• Hollow bones: Reduce weight

• Fused bones and keeled sternum for flight muscle attachment

• High metabolism and efficient lungs with air sacs

20. Mammal Evolutionary Descent:

• Descended from synapsid ancestors (e.g., Dimetrodon)

• Evolved traits like hair, mammary glands, and differentiated teeth

• True mammals arose during the Mesozoic; diversified after dinosaur extinction

21. Three Main Groups of Mammals:

22. Major Eutherian Clades & Characteristics:

23. Derived Primate Features:

• Grasping hands and feet

• Flat nails (not claws)

• Forward-facing eyes (depth perception)

• Large brain relative to body

• Social behavior and parental care

24. Old World vs. New World Monkeys: