Lecture:1

Where did life first begin?

Life began in a marine environment.

What percentage of phyla are entirely marine?

More than half of all phyla are entirely marine.

Why have most invertebrates been less successful on land than arthropods?

Because water provides physical support, stability, and moisture that land environments lack.

What are the five main benefits of living in a marine environment?

Gas exchange, reproduction, mobility, excretion, and thermal stability.

How does reproduction occur in marine environments?

Through external fertilization where gametes and zygotes get nutrients from the environment.

What adaptations are needed for reproduction on land?

Internal fertilization and protective provisioning for zygotes or eggs.

Why is movement easier in water?

Water supports body weight, allowing sessile lifestyles and less energy use.

What mobility adaptations are necessary for land animals?

Support structures like skeletons and increased musculature for movement.

How do marine animals excrete waste?

They release ammonia directly into the water, where it diffuses away.

How do terrestrial animals handle excretion differently?

They convert ammonia into urea or uric acid and use specialized organs to conserve water.

Why is temperature regulation easier in water?

Water has high thermal stability, keeping body temperatures constant.

What adaptations are needed for temperature control on land?

Behavioral regulation and endothermy (being 'warm-blooded').

What are the five main challenges of marine life?

Pressure differences, light limitation, low oxygen, high viscosity, and pollutants.

How do deep-sea animals handle pressure changes?

Through unique physiology and behaviors that keep them at stable depths.

Why is light a challenge in the ocean?

Light only penetrates 20–50 meters, limiting photosynthesis.

What adaptations help organisms survive in low light?

Chemosynthesis or symbiotic relationships with photosynthetic organisms.

Why is oxygen a challenge in marine environments?

Water holds less oxygen than air.

How do marine animals adapt to low oxygen?

They live near currents or generate water movement to increase oxygen flow.

How do marine animals cope with the density of water?

They have streamlined bodies for efficient movement.

Why are pollutants a problem for marine animals, especially larvae?

Pollutants can damage delicate tissues and disrupt development.

What are the three main challenges of freshwater life?

Osmotic pressure, ephemeral habitats, and changing pH/temperature.

How do freshwater animals adapt to osmotic pressure?

They regulate ions and prevent excess water from entering their bodies.

What do animals do when freshwater habitats dry up?

Enter dormant stages or produce protective eggs.

What are some pre-adaptations that allowed animals to move onto land?

Internal fertilization, protective coverings, and desiccation-resistant eggs.

Where can you find a summary of aquatic vs. terrestrial adaptations?

In Table 1.1 of the textbook.