Question

Which of the following evolutionary innovations was advantageous for survival in a terrestrial environment? a. the amniotic egg in animals b. the seed in plants c. the shell in marine invertebrates d. all of the above e. both a and b

Short answer

The correct choice is: (e) both a and b

Step-by-step solution

Understand the question and the choices

The exercise asks which evolutionary innovations were advantageous for survival in a terrestrial environment. The given options are: (a) the amniotic egg in animals, (b) the seed in plants, (c) the shell in marine invertebrates, (d) all of the above, and (e) both a and b.

Analyze each choice separately

Analyze each option separately: \n \n (a) Amniotic egg : It is an evolutionary innovation in reptiles, birds and mammals, allowing them to lay their eggs on land without fear of desiccation. This gave these animals the ability to live away from water bodies.\n \n (b) Seed: The evolution of seeds allowed plants to survive in different environmental conditions and they could spread over larger areas. Seeds carry their own food supply and can remain dormant under unfavourable conditions, enabling plants to overcome time. \n \n (c) Shell in marine invertebrates: Shells are mainly a characteristic of aquatic animals. The shell provides protection against predators, and helps in buoyancy, not a benefit for land survival.

Find and justify the right answer

Both amniotic egg and seed are adaptations that allowed animals and plants respectively to survive on land. So, the correct answer is (e) both a and b. Shells are not typically a survival mechanism for terrestrial environment but rather for the aquatic life.

Key concepts

Amniotic Egg

The amniotic egg is a crucial evolutionary breakthrough that allowed certain groups of animals, such as reptiles, birds, and mammals, to thrive on land. This adaptation involves an egg that is equipped with several protective layers and a nutrient-rich yolk. The outer shell of the amniotic egg is semi-permeable, which allows for gas exchange while preventing desiccation.
The amniotic egg includes:

• An amnion, which provides a protective fluid-filled space for the developing embryo.
• An allantois, which handles waste materials and facilitates respiration.
• A chorion, which expands around the other membranes and assists in gas exchange.

This innovation meant that land animals were no longer bound to water for reproduction. This was a transformative step in vertebrate evolution, allowing species to move away from aquatic environments and dominate terrestrial habitats. Hence, the amniotic egg was pivotal in supporting these animals' successful transition to land.

Seed Dispersal

Seed dispersal represents a major evolutionary step for plants, allowing them to colonize new environments away from their parent plants. Seeds have various mechanisms that enable them to travel far and wide.

• Wind: Light seeds with wing-like structures that can be dispersed by the wind.
• Animals: Fleshy fruits attract animals that eat them and disperse seeds through droppings.
• Water: Buoyant seeds that can float and travel via water bodies.
• Mechanical: Some plants have explosive mechanisms that shoot seeds away.

The key to seed dispersal is not just transportation but also ensuring that seeds land in a suitable environment for growth. Inside the seed, there is stored food to nourish the emerging plant, and a tough outer coat protects it from harsh conditions. Seed dormancy allows plants to withstand unfavorable conditions until they are right for germination. The combination of these strategies has allowed seed-bearing plants to dominate a variety of landscapes and climate zones, securing their survival and expansion.

Evolutionary Innovations

Discussing evolutionary innovations, these are the traits that emerged over time enabling organisms to adapt more effectively to their environments. Such innovations can lead to increased survival and reproductive success.
Two significant evolutionary innovations highlighted in terrestrial adaptation include:

• The amniotic egg, granting vertebrates the freedom to reproduce away from aquatic settings.
• The seed, facilitating the spread and survival of plants in diverse environments.

These innovations underscore the intertwined evolution of plant and animal life as each responded to the challenges and opportunities of terrestrial life. By overcoming the limitations imposed by reliance on water, both seeds and amniotic eggs represent key milestones that allowed extensive diversification and complexity of life on land. These innovations showcase nature's remarkable ability to solve survival challenges, illustrating the adaptive power of evolution.