Paddlefishes and Sturgeons

• Paddlefishes are rare fish found in the Upper Midwest; they can grow to be large.
• Sturgeons are a picture reference to compare size and rarity with paddlefishes.

Basal Actinopterygi

• Groups include Gars and Bowfins, characterized by big fleshy fins.
• Both groups are considered Osteichthyes (bony fish).

Osteichthyes Identification

• Standard body form for Osteichthyes:
  • Represents 95% of all fish.
  • Most are teleosts (a subgroup).

Buoyancy Control

• Regulation achieved via the swim bladder, which is derived from lungs.
• Fish capture oxygen through gills, which fills the swim bladder:
  • Allows fish to ascend by taking in more gas, or descend by releasing gas.
• The operculum is a bony plate that covers the gills, unique to Osteichthyes.
• Fins possess bilateral symmetry with paired fins beneath the body.

Morphological Diversity of Fish

• Fish exhibit considerable morphological diversity:
  • Examples include flatfish, which undergo developmental changes causing eye migration to one side of their body during their life cycle.
• Flounders showcase this adaptation clearly during their lifecycle moving from symmetrical to asymmetrical forms.

Seahorses and Pipefish

• They possess features common to Osteichthyes, including swim bladders and operculum.
• Fish demonstrate vast diversity in shape and sizes.

Actinopterygia vs. Sarcopterygii

• Actinopterygia (Ray-finned fishes) are the most diverse.
• Sarcopterygii (Lobe-finned fishes) include lungfishes and coelacanths:
  • Coelacanths were considered extinct until discovered in 1936, resembling fossils from 300 million years ago.
  • Sarcopterygii gave rise to tetrapods, indicative of an evolutionary transition.

Evolution of Tetrapods

• The transition: from fish to tetrapods involves significant anatomical adaptations:
  • Development of heavier bones for terrestrial support.
  • Lungs evolved for breathing air instead of relying on gills.
• Early tetrapods dealt with moisture, skin adaptations, and changes in sensory perception as they left water environments.

Characteristics of Early Amphibians

• Early amphibians retain several adaptations for life both in water and on land, like moist skin for respiration, and reproductive strategies involving water-laying eggs.
• Three main lineages include:
  1. Anura – Frogs and toads.
  2. Caudata – Salamanders and newts.
  3. Gymnophiona – Caecilians (lesser known but interesting).

Amniotes and Adaptations for Dry Land

• Amniotes describe organisms that lay eggs on land, marking a significant evolutionary adaptation away from water dependency.
• Their skin evolves to be keratinized and lipid-rich to retain moisture effectively.
• Amniotic eggs contain yolk and a protective, hard outer shell, providing nutrients and safeguarding against dehydration.

Major Lineages of Amniotes

• Synapsids (Mammals) and Reptiles are key groups:
  • Reptiles split into:
  • Lepidosaurs (most notably squamates like lizards and snakes).
  • Archosaurs (crocodiles, dinosaurs, and birds).
• Major adaptations in reptiles include keratinized skin and behaviors for temperature regulation through their environments.

Birds and Unique Adaptations

• Birds are adapted for flight with features like hollow bones and feathers:
  • Feathers provide lift, insulation, and waterproofing.
  • RAM ventilation in lungs aids oxygenation, crucial for their high metabolism.

Evolutionary Significance of Synapsids (Mammals)

• Mammals developed several adaptations that support life:
  • Fur, lactation, high metabolic rates to maintain body temperature, and efficient four-chambered hearts.
  • Parental care distinguishes mammals from other classes via extended care, improving offspring survival.

Classification of Mammals

• Three major groups:
  1. Monotremes – Egg-laying mammals (e.g., platypus).
  2. Marsupials – Carry and nurse young in pouches.
  3. Eutherians – Placental mammals (largely represented in diversity).

Primates and Human Evolution

• Primates include humans, apes, and monkeys, characterized by:
  • Flexibility in hips and shoulders allowing for erect posture.
  • Grasping hands and forward-facing eyes.
• Two major primate lineages: Strepsirrhini (lemurs, lorises) and Haplorhini (monkeys, apes).

Human Ancestry

• Key insights into human evolution involve:
  • Shared lineage with Chimps, the closest living relatives.
  • Significant periods of human diversification occurred in Africa over the past seven million years, including species like Australopithecines and Homo erectus.