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.