Skeletal Adaptations:
* Stronger limbs: Water provides buoyancy, so land animals needed stronger limbs and skeletal structures to support their weight and move efficiently on land.
* Rib cage: Developed to protect internal organs, as land animals were no longer supported by the water's buoyancy.
* Joints: More complex and mobile joints for greater flexibility in locomotion.
Respiratory Adaptations:
* Lungs: Developed to extract oxygen from the air, replacing gills which are inefficient in air.
* Diaphragm: Muscle that helps with breathing by expanding the lungs, a key innovation for efficient air breathing.
Circulatory Adaptations:
* Four-chambered heart: This allows for separate circulation of oxygenated and deoxygenated blood, providing greater efficiency for delivering oxygen to tissues and removing carbon dioxide.
* Efficient blood vessels: Network of blood vessels with thicker walls and greater pressure to circulate blood effectively against gravity.
Sensory Adaptations:
* Ears: Developed to detect sound vibrations in air, replacing lateral lines used in water.
* Eyes: Adapted for vision in air, including features like eyelids and tear glands.
* Smell and taste: More developed sense of smell and taste to find food and navigate their environment.
Reproductive Adaptations:
* Internal fertilization: Essential for reproduction on land, protecting eggs from drying out.
* Amniotic egg: Watertight egg with a shell and internal membranes, providing a self-contained environment for developing embryos.
Other Adaptations:
* Skin: Developed a thicker skin to prevent dehydration and protect against injury.
* Water conservation: Specialized kidneys and excretion mechanisms to conserve water, crucial in a dry environment.
Important Note: These adaptations didn't all evolve at once. The transition from water to land was a gradual process over millions of years, with different groups of vertebrates developing different adaptations at different times. Some adaptations arose earlier than others, and some groups of vertebrates retained certain aquatic features even after becoming land-based.