Have you ever wondered why most animals munch on leaves, fruits, and seeds from trees but rarely eat wood? It turns out that wood is a tough nut to crack, and only a few creatures, mainly insects, have figured out how to do it. Let’s explore why wood isn’t a popular snack in the animal kingdom.
Wood is made up of cellulose, a nutritious carbohydrate found in many parts of plants. However, cellulose in wood is tightly bound by a complex molecule called lignin. This makes wood incredibly strong and hard to digest. While some animals, like beavers, have sharp teeth and strong jaws to gnaw on wood, they can only break it down partially. Most of the cellulose remains trapped in lignin and passes through their system undigested.
Insects like termites are the real wood-eating champions. They have special tools and helpers to get the job done. Termites have serrated mandibles, which are like tiny saws, to chew through wood. More importantly, they have special microbes in their guts that can break down lignin at the molecular level, freeing up the cellulose for digestion.
Lignin didn’t just evolve to make wood strong; it also acts as a defense mechanism for plants. It makes it difficult for most microbes to break down wood. However, over millions of years, some microbes have developed enzymes that use oxygen to break the bonds in lignin molecules. This process is crucial for decomposing wood in nature.
Termites have managed to incorporate these lignin-decomposing microbes into their guts, allowing them to digest wood efficiently. Why haven’t more animals done the same? It might be due to the unique chemical environment in their guts or the presence of other microorganisms that aren’t welcoming to new microbes. It’s also possible that termites are just ahead of the game, and in the future, more animals might evolve to eat wood.
This fascinating topic is explored by researchers like Professor Tom Bourguignon at the Okinawa Institute of Science and Technology Graduate University (OIST). His lab studies the DNA of termite gut microbes to understand how these insects have become so successful in digesting wood. OIST is an international graduate school in Japan that supports young scientists in their research endeavors.
So, while wood remains a challenging food source for most animals, the few that have cracked the code offer a glimpse into the incredible adaptability and evolution of life on Earth.
Using materials like cardboard, string, and glue, create a model representing the structure of wood, focusing on cellulose and lignin. This will help you visualize why wood is tough to digest. Present your model to the class and explain how lignin protects cellulose.
Research the digestive system of termites and create a simulation using a simple experiment. Use a plastic bottle to represent the termite’s gut and materials like vinegar and baking soda to mimic the chemical reactions involved in breaking down wood. Share your findings with the class.
Participate in a role-playing game where you take on the role of different animals and insects. Discuss and debate the advantages and challenges of eating wood. This activity will help you understand the evolutionary adaptations required for wood digestion.
Conduct a research project on the microbes that assist termites in digesting wood. Create a presentation or poster that explains how these microbes work and their importance in the ecosystem. Present your project to the class.
Imagine you are a journalist interviewing a scientist like Professor Tom Bourguignon. Prepare a list of questions about termite digestion and their microbial helpers. Role-play the interview with a classmate, focusing on the scientific insights gained from studying termites.
Here’s a sanitized version of the transcript:
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While animals across the animal kingdom consume nearly every part of trees—leaves, fruits, flowers, seeds, and even their internal fluids—wood is primarily eaten by a few insects. What prevents other animals from consuming wood? Although wood contains cellulose, the same nutritious carbohydrate found in other edible tree parts, it is largely bound by a complex molecule called lignin. This structure makes wood strong on both the molecular and macro levels, making it difficult to eat.
Some animals, like beavers, possess the necessary adaptations, such as sharp teeth and strong jaws, to break down wood at the macro level, which releases some cellulose. However, much of it remains undigested and is excreted still entangled in lignin. Insects like termites can consume wood effectively because they have serrated mandibles to chew it and the appropriate gut microbes to break down lignin at the molecular level.
Lignin evolved partly as a defense mechanism for plants against attackers, particularly independent microbes, which has made it challenging for most microbes to break it down. However, after millions of years, some microbes have developed enzymes that utilize oxygen to break the bonds in lignin molecules, freeing the cellulose for consumption. This process is essential for wood decomposition.
For termites and a few other insects to digest wood, they had to adapt these independent lignin-decomposing microbes into gut-dwelling ones. The reasons why more animals haven’t been able to harness these microbes remain unclear; it could be due to the chemical composition of their guts or the presence of other microorganisms that are not conducive to newcomers. It’s also possible that termites are pioneers in this regard, and future evolution may lead to a greater diversity of wood-eating animals.
This video was sponsored by the Okinawa Institute of Science and Technology Graduate University, an international graduate school dedicated to advancing science, education, and innovation in Japan and globally. OIST offers a fully-funded PhD program and research internship opportunities that attract talented young scientists from around the world to collaborate with researchers like Professor Tom Bourguignon, whose Evolutionary Genomics lab studies how insects have thrived in terms of biomass and biodiversity. The lab’s research on termite gut microbe DNA contributed to this video, revealing how wood-digesting microbes have evolved, with some existing exclusively within termites.
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This version maintains the essential information while ensuring clarity and professionalism.
Wood – The hard, fibrous material that forms the main substance of the trunk or branches of a tree or shrub, used for structural support and nutrient transport. – Trees rely on wood to transport water and nutrients from their roots to their leaves.
Cellulose – A complex carbohydrate that forms the main component of the cell walls in plants, providing structural support. – Cellulose is a major component of plant cell walls, giving them strength and rigidity.
Lignin – A complex organic polymer found in the cell walls of many plants, making them rigid and woody. – Lignin helps plants stand upright by providing additional support to their cell walls.
Insects – A class of small arthropods with a three-part body, usually having wings and antennae, that play various roles in ecosystems. – Insects like bees are crucial for pollinating many types of plants.
Termites – Social insects that feed on wood, often causing damage to wooden structures, but also playing a role in decomposing dead plant material. – Termites help recycle nutrients in the ecosystem by breaking down dead wood.
Digestion – The process by which organisms break down food into smaller components that can be absorbed and used for energy and growth. – In humans, digestion begins in the mouth with the breakdown of carbohydrates by enzymes.
Microbes – Microscopic organisms, including bacteria, viruses, and fungi, that can have beneficial or harmful effects on other living organisms. – Microbes in the soil play a vital role in decomposing organic matter and recycling nutrients.
Carbohydrates – Organic compounds made up of carbon, hydrogen, and oxygen, serving as a major energy source for living organisms. – Plants produce carbohydrates through photosynthesis, which are then used as energy by animals that consume them.
Evolution – The process by which different kinds of living organisms develop and diversify from earlier forms over generations. – The evolution of the peppered moth is a classic example of natural selection in response to environmental changes.
Environment – The surrounding conditions in which an organism lives, including air, water, soil, and other living things. – The environment of a rainforest is characterized by high humidity and diverse plant and animal species.
