Question

Suggest at least one reason plants moved onto land before large animals.

Short answer

Plants could photosynthesize, needed fewer adaptations, and faced less competition on land.

Step-by-step solution

Understand the Characteristics of Plants

Plants have certain traits that would have allowed them to survive on land before large animals. For example, they can perform photosynthesis, which means they do not rely on other organisms for food. They also can anchor themselves to the ground using roots, which might have allowed them stability in terrestrial environments.

Consider the Advantages of Land for Plants

Land provides access to sunlight, which is a vital resource for photosynthesis. Plants on land also faced fewer competitors and predators compared to marine environments, giving them an evolutionary advantage.

Analyze Animal Requirements

Large animals generally require more complex adaptations to survive on land, such as specialized respiratory and locomotion systems. These adaptations likely took more evolutionary time to develop than the changes needed by plants.

Key concepts

Terrestrial Adaptation

Plants underwent significant transformations to thrive on land. One key adaptation was the development of a cuticle, a waxy layer covering the plant's surfaces. This protective layer helped prevent water loss, crucial for survival in drier terrestrial climates.
Roots also played a pivotal role by not only anchoring plants in the soil but also facilitating the uptake of water and nutrients.
Another important adaptation was the development of stomata. These small openings helped regulate gas exchange by allowing carbon dioxide to enter for photosynthesis while reducing water loss.

Additionally, the strength and structure provided by lignin in cell walls supported plant bodies against gravity. These adaptations collectively enhanced the plant's ability to colonize land and harness its resources effectively.

Photosynthesis

Photosynthesis is the process by which plants convert light energy into chemical energy, which fuels their growth and reproduction. On land, plants had better access to sunlight than in aquatic environments.

This gave them a clear advantage, allowing for efficient photosynthesis and making land colonization feasible. Photosynthesis involves two main stages:

• Light-dependent reactions – these occur in the chloroplasts and require sunlight to produce energy-rich molecules like ATP and NADPH.
• Calvin cycle – uses these energy-rich molecules to convert carbon dioxide into glucose, a sugar that plants use for energy and structure.

Additionally, land offers less competition for light compared to the dense underwater environments, providing a strong incentive for plants to establish themselves on terrestrial grounds.

Evolutionary Biology

Evolutionary biology helps us understand how plants developed the features necessary to live on land. The transition from aquatic to terrestrial life marked a significant evolutionary milestone. It was driven by environmental changes and natural selection.

Plants that could efficiently take advantage of sunlight, manage water loss, and access soil-bound nutrients were more likely to survive and reproduce. Over time, these advantageous features became more common within plant communities.
Key shifts included:

• Development of vascular tissues like xylem and phloem for efficient transport of water and nutrients.
• Reproductive strategies such as seeds and spores, which enabled plants to spread and thrive in varied environments.

Evolutionary biology provides a framework to understand not just the hows but also the whys behind these elaborate adaptations.

Land Colonization

The shift of plants from water to land represents a pivotal moment in evolutionary history. This colonization was driven by several factors that provided plants with an advantage over life in aquatic settings.

On land, plants could access abundant sunlight, face fewer aquatic predators, and encounter new niches with less competition. Although terrestrial life posed challenges like water scarcity, the benefits outweighed the drawbacks. Here are a few key points:

• The relatively fewer herbivores on land at the time meant plants faced less predation.
• Less competition allowed for expansive growth and territorial establishment.

The ability to photosynthesize independently and anchor to the ground gave plants the functional tools to succeed in new terrestrial ecosystems, setting the stage for myriad life forms to eventually follow.