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Journey Through Animal Evolution: Unique Characteristics and Trends Explored

Explore the fascinating world of animal evolution, from colonial flagellated protists to complex multicellular organisms. Discover the key characteristics such as heterotrophic eukaryotes, lack of cell walls, nervous and muscular tissues, and regulatory genes like Hox genes. Uncover trends like multicellularity, symmetry and tissue development, bilateral symmetry with internal organs and cephalization, body cavity formation, coelom evolution, segmentation, and deuterostome development. Delve into the intriguing evolution of animals through the lens of key trends and features that have shaped their diversity.

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Journey Through Animal Evolution: Unique Characteristics and Trends Explored

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  1. Introduction to Animal Evolution

  2. Define: animal Unique characteristics: Heterotrophic eukaryotes; ingestion Lack cell walls; collagen Nervous & muscular tissue Sexual; diploid; cleavage; blastula; gastrulation; larvae; metamorphosis Regulatory genes: Hox genes

  3. Trend #1Multicellularity Monophyletic Group colonial flagellated protist ancestor=choanoflagellates

  4. Trend #1: Multicellularity Hypothesis for the evolution of animals from a colonial protist ancestor-

  5. 9

  6. Trend #2: Symmetry and Tissue • Radial Symmetry: • Cnidaria (hydra; ‘jellyfish’; sea anemones) • Ctenophora (comb jellies)~ radial body symmetry

  7. Trend #2: Symmetry and Tissue Parazoa-Eumetazoa dichotomy: • sponges (Parazoa)~ no true tissues • all other animals (Eumetazoa)~ true tissues Diploblastic: Endoderm Ectoderm Triploblastic: Endoderm Mesoderm Ectoderm

  8. Eumetazoa

  9. Trend #3 Bilateral Symmetry, Internal Organs, Cephalization

  10. Trend #3 Bilateral Symmetry, Internal Organs, Cephalization • Bilateral Symmetry: • DORSAL • VENTRAL • ANTERIOR • POSTERIOR • Internal Organs • Cephalization • -Progressive increase in nerve tissue at anterior end as organisms increase in complexity

  11. Trend #4: Body Cavity

  12. Trend #4: Body Cavity • Gastrovascular Cavities (GUTS) are where food is digested, two openings designate a digestive tract • A body cavity is a fluid filled space separating the digestive tract from the outer body wall • Animals without a cavity between the digestive tract and the outer body wall are called ACOELOMATES

  13. Trend # 5: Coelom • Embryonic development in more advanced animals, a cavity called a coelom develops from tissue developed from mesoderm germ layer • Cushions internal organs, allows for expansion and contraction

  14. Trend # 5: Coelom • Acoelomate, Pseudocoelomate, and Coelomate Grades: • triploblastic animals~ solid body, no body cavity; called acoelomates (Platyhelminthes-flatworms) • body cavity, but not lined with mesoderm; called pseudocoelomates (Rotifers, Nematodes) • true coelom (body cavity) lined with mesoderm; called coelomate

  15. Trend # 6: Segmentation • Insects and Certain worms= segmented body parts • Some body parts repeat, others are adapted for specific functions

  16. (Trend #7: Jointed Appendages and Exoskeleton) • Skeleton on the outside, needs to be shed to grow • “Jointed foot”-legs, antennae, mouthparts

  17. Trend #8 Deuterostome Development • Protostome-Deuterostome dichotomy among coelomates: • protostomes (mollusks, annelids, arthropods) • deuterostomes (echinoderms, chordates) • During early development of zygote, cell divisions, or cleavages occur • Specific cleavage patterns occur • 2 development patterns occur in two groups of animals:

  18. Trend #8 Deuterostome Development Protostome-Deuterostome dichotomy among coelomates: a) cleavage: protostomes~ spiral and determinate deuterotomes~ radial and indeterminate b) coelom formation: protostomes~ schizocoelous; deuterostomes~ enterocoelous c) blastopore fate: protostomes~ mouth from blastopore; deuterostomes~ anus from blastopore

  19. Trend # 9: Notochord

  20. Trend # 9: Notochord

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