Evolution of insects

Insects have lived on Earth for a very long time.

They may have started from small water creatures. Long ago, the first insects lived on land. Then, some insects grew wings to fly.

This made them the first animals to fly. Many insects lived in warm, wet swamps.

Some insects even grew to live with flowers. They help flowers grow by moving pollen. Insects are a big part of our world.

Insects have a very long history on Earth. They may have started from a group of water creatures called crustaceans.

Scientists think insects first appeared about 480 million years ago. Most insects lived on land at first. About 400 million years ago, some insects grew wings. They became the first animals to fly.

Many groups of insects changed over time. Some insects went extinct during a large mass extinction. This happened about 252 million years ago. The survivors grew into the insect groups we see today. Many modern insect families appeared during the Jurassic period.

Insects and flowers grew up together. This is called co-evolution. This means the two groups changed in ways that helped each other. For example, many insects eat nectar or pollen.

About 20% of insects today rely on flowers for food. Many flowers also need insects to help them grow. We can learn about this history from fossils. Some insects are even found inside amber. Amber is hard tree resin.

These fossils can show perfect details.

Insects are some of the most successful living things on our planet. They have changed and grown in many amazing ways over millions of years. Scientists study these changes using many different tools. They look at tiny parts of cells and old fossils in rocks. They even use computers to understand how insects evolved. This long history helps us see how life adapts to a changing world.

How do insects change over time? It often starts with how they interact with their surroundings. For example, many insects evolved alongside flowering plants. This is called co-evolution, where two groups change together to help each other. Some insects eat nectar or pollen from flowers. In return, more than two-thirds of flowering plants rely on insects to help them grow. This partnership has helped both groups succeed for a very long time.

The history of insects is incredibly old. Scientists think the first insects appeared about 480 million years ago. They likely evolved from a group of water creatures called crustaceans. Most early insects lived on land. About 400 million years ago, during the Devonian period, some insects grew wings. These were the very first animals to fly.

Earth has seen many big changes since then. About 252 million years ago, a huge mass extinction occurred. This was the largest extinction event in Earth's history. Many early insect groups did not survive this event. However, the survivors evolved into the modern insect orders we see today. Most modern insect families appeared later during the Jurassic period.

We learn about this history by looking at fossils. Some insects are preserved in amber, which is hard tree resin. These fossils can show perfect details, like colors or patterns. Other insects are found in lake sediments or special rocks called limestones. Some fossils are even made when minerals replace the insect's body. This is called mineral replication. These tiny treasures show us exactly how insects lived long ago.

Insects are among the most diverse and successful groups of animals on Earth. Their long history is a story of constant adaptation to a changing planet. Scientists study this history through many different scientific lenses. They use molecular biology to look at DNA and morphology to study body shapes. They also use paleoentomology, which is the study of insect fossils, to piece together the past. By combining these fields with bioinformatics and embryology, researchers can reconstruct how insects became the creatures we see today.

The evolutionary journey of insects likely began hundreds of millions of years ago. Many scientists believe insects evolved from a group of crustaceans. Molecular analysis suggests that hexapods, or six-legged animals, diverged from their relatives around the start of the Silurian period. This timing coincides with the appearance of vascular plants on land. While some researchers argue insects appeared even earlier during the Ordovician period, this remains a controversial idea. This is because there is a lack of insect fossils from the Cambrian or Silurian periods to prove it.

As insects moved onto land, they underwent several major evolutionary stages. The first insects were landbound, but the Devonian period brought a massive change. About 400 million years ago, one lineage of insects evolved flight. These were the very first animals to ever fly. Later, during the Carboniferous period, which lasted from 358 to 299 million years ago, the Pterygotes, or winged insects, underwent a major radiation. This means they rapidly diversified into many new forms. Following this, the Endopterygota, which are insects that go through distinct life stages via metamorphosis, radiated during the Permian period.

Earth's history has been marked by dramatic shifts in climate and life. About 252 million years ago, the Permo-Triassic boundary saw the largest mass extinction in Earth's history. Many early insect groups were lost during this event. However, the survivors evolved during the Triassic period into the modern insect orders we recognize today. Most modern insect families appeared during the Jurassic period, between 201 and 145 million years ago. By the Cretaceous period, many insect groups began to evolve alongside flowering plants. This process is known as co-evolution, where two different groups change together in a way that affects both. Today, about 20% of extant insects depend on flowers, nectar, or pollen for food. In return, more than two-thirds of flowering plants rely on insect pollination to reproduce.

Understanding this history requires a deep look at how insects become fossils. Because insects are small and light, they do not always leave a strong fossil record. Only about 1/100 of known insect species are represented in the fossil record. Most insect fossils are found in lake environments, known as lacustrine settings. Insects might live in the lake or be carried into it by wind or water. If they die and settle into anoxic, or oxygen-poor, sediments, they may be preserved. Some insects are preserved as compressions or impressions in rocks. These show the shape of the insect, sometimes even the texture of the wing membranes.

Other fossils are much more detailed. Some insects are preserved in amber, which is fossilized tree resin. This type of preservation became abundant during the Mesozoic era. Amber can capture insects in perfect condition, sometimes even preserving their original color and patterns. Another method is mineral replication, or petrifaction. This happens when minerals replace the insect's body, often creating a three-dimensional replica. Some fossils are also found as concretions, which are stones with a fossil at the core. These form when minerals precipitate around a decaying organism. These diverse preservation methods allow scientists to study everything from ancient feeding damage to fossilized nests and fecal pellets.

Insects continue to play a vital role in global ecosystems. Their ability to fill available environmental niches is driven by rapid adaptation and high fecundity, which is the ability to produce many offspring. While many insects are helpful pollinators, others act as vectors for pathogens. Some insects, like flies and mosquitoes, can spread diseases that have impacted other species. Despite these complexities, the evolutionary success of insects is undeniable. They have survived massive extinctions and shaped the very plants they live upon, creating a complex web of life that continues to evolve every day.