PH

Lecture+ 17

Deuterostome Animals: Tetrapods

Overview

  • Focus on Chapter 32, pages 684-696, with specific attention to Figures 32.8, 32.15, 32.16, 32.19, Table 32.6.

Learning Outcomes

  • 17.1 Describe major innovations in tetrapod evolution.

  • 17.2 Recognize traits of the major tetrapod groups (amphibians, mammals, reptiles, including birds).

  • 17.3 Compare human characteristics to other primates and mammals.

  • 17.4 Evaluate human evolution insights from fossil and molecular evidence.

Vertebrate Innovations

Key Innovations in Chordata

  • Pharyngeal Slits: Present in chordates, lost in some phyla.

  • Chordata Characteristics:

    • Dorsal hollow nerve cord

    • Notochord

    • Muscular post-anal tail

    • Cranium and vertebrae

    • Paired sense organs

  • Loss of Features in Other Phyla:

    • Echinodermata & Hemichordata: Loss of pharyngeal slits.

    • Urochordata (Tunicates): Loss of vertebrae.

Major Groups in Chordata

  • Vertebrates: Include all major animal groups, with a focus on three-part brain, lungs, jaws, and paired appendages.

  • Key Groups:

    • Actinopterygii (Ray-finned fishes)

    • Chondrichthyes (Sharks, rays)

    • Sarcopterygii (Lobed fins)

    • Tetrapoda (includes amphibians, reptiles, mammals)

Species Richness and Vertebrate Diversity

  • Vertebrates highly diverse, incorporating:

    • Ray-finned fishes

    • Half fishes and half tetrapods

    • Includes amphibians, mammals, and reptiles.

Key Innovations in Tetrapods

  1. Limbs: Adaptive radiation during the transition from water to land.

  2. Amniotic Eggs:

    • Reduces drying, allows for larger eggs compared to amphibians.

    • Four membranes provide support and protection.

  3. Lactation and Fur: Key innovations leading to thermoregulation and care for offspring.

Amphibia

  • Groups include frogs, toads, and salamanders; most species lay eggs in water.

  • Chytrid Fungus Threat: ~8500 species with ~500 extinct due to chytridiomycosis; over 40% are globally threatened.

Mammalian Lineages

  • Three Lineages:

    • Monotremes: Egg-laying mammals.

    • Marsupials: Development in pouches.

    • Placentals: Most mammals with gestation in a placenta.

Key Innovations in Mammals

  1. Lactation: Milk production by mammary glands.

  2. Fur: Insulated coat made from keratin.

Evolution of Reptiles and Birds

  • Key characteristics include scales, amniotic eggs, and evolutionary links to birds from dinosaurs.

  • Evolution of Flight: Feathers provide insulation and facilitate flight.

Human Evolution

Primate Traits

  • Characteristics include grasping limbs, large brains, and complex social behaviors.

  • Two groups of primates:

    • Prosimians: e.g., tarsiers and lemurs.

    • Anthropoids: e.g., monkeys, gibbons, great apes including humans.

Hominin Evolution

  • Hominins: monophyletic group including Homo sapiens and over 20 extinct relatives.

  • Key extinct species: Homo erectus, Homo neanderthalensis, known for cultural and social behaviors.

  • Out-of-Africa Hypothesis: Evolution and migration patterns of Homo sapiens.

Contemporary Human Evolution

  • Genetic Mutations: Variations include lactose persistence and malaria resistance through red blood cell disorders.

  • Bacterial Co-evolution: Human gut bacteria show symbiotic relationships linked to great apes.