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Sundews have mucus tipped hairs to catch unsuspecting bugs. The mucus is super sticky—and sweet to attract prey. Carnivorous plants use enzymes to digest their meals. Sundews know if they’ve caught a treat or a trick! Non-nutritious things may get stuck, but the sundew will toss them aside.

 

Willi Rolfes/McPhoto/Ullstein Bild via Getty Images

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Killer Plants

Learn how carnivorous plants evolved to get their nutrients from sources other than soil

A fly buzzes over a swamp and catches the sweet scent of nectar. Following the scent to its source, the fly lands on a bright-red leaf and—SNAP! It’s trapped between the leaves of a Venus flytrap. Over the next 5 to 12 days, the plant will digest its meal.

Why does the Venus flytrap do this? The swampy soil where it lives lacks important nutrients the plant needs in order to grow. That means it must turn to another source: insects.

A fly buzzes over a swamp. It notices the sweet smell of nectar. Following the scent to its source, it lands on a bright-red leaf. Suddenly—SNAP! The fly is trapped between the leaves of a Venus flytrap. Over the next several days, the plant will digest its meal.

Why does the Venus flytrap do this? It lives in swampy soil, which lacks nutrients the plant needs in order to grow. So the plant turns to another source: insects. 

Alex Hydeq/NaturePL (venus flytrap); (C)ImageBroker/Markus Keller/Biosphoto (sundew leaf)

A Venus flytrap snap shut in one-tenth of a second to trap a tasty fly. (left) A sundew’s leaf curls around its prey to start digesting. (right)

CREATING CARNIVORES

The Venus flytrap is one of more than 800 known species of carnivorous plants. All carnivorous plants grow in places with nutrient-poor soil. Over millions of years, these plants developed adaptations that allow them to digest insects, spiders, and more. These prey provide the plants with the nutrients they need to grow.

British naturalist Charles Darwin was fascinated by carnivorous plants. He spent 16 years studying them before publishing his book Insectivorous Plants in 1875. “Darwin recognized that carnivorous plants were substituting animal prey for nutrients they would typically get from the soil,” says Thomas Givnish, a botanist at the University of Wisconsin.

Carnivorous plants are a perfect example of one of Darwin’s theories of evolution, called convergent evolution. In convergent evolution, similar environmental factors cause the same traits to evolve among unrelated ancestors. “Carnivorous plants have 10 separate origins,” says Givnish. At least one species of carnivorous plant can be found on every continent except Antarctica.

Venus flytraps are carnivorous, or meat-eating, plants. Over millions of years, they developed the ability to digest insects, spiders, and more. These prey provide important nutrients that the plants would normally get from the soil. There are more than 800 known species of carnivorous plants. 

The famous British scientist Charles Darwin was fascinated by carnivorous plants. He spent 16 years studying them and published a book about them in 1875. “Darwin recognized that carnivorous plants were substituting animal prey for nutrients they would typically get from the soil,” says Thomas Givnish. He’s a plant scientist at the University of Wisconsin.

Darwin is known for his theory of evolution. It describes how species change over time to better fit their environments. Carnivorous plants are a perfect example of this, says Givnish. At least 10 different types of plant that grow in nutrient-poor soil have evolved to eat insects. Now carnivorous plants can be found on every continent except Antarctica! 

GOTCHA!

Plants can’t move around like animal predators. Since they’re stuck in one place, carnivorous plants have sneaky adaptations to lure, trap, and digest prey.

Usually plants produce nectar to attract pollinators that will transport pollen from plant to plant so the plants can reproduce. But carnivorous plants use nectar to kill. An insect will land on a leaf expecting a meal . . . only to find it’s their last!

Plants can’t move around to hunt like animals can. So carnivorous plants use other tricks to snag their prey. They mostly grow in sunny and moist places where there are a lot of insects. The sunlight gives the plants energy to grow the traps they use to catch prey.

Most plants make nectar to attract pollinators. These insects carry pollen from plant to plant as they feed, helping the plants reproduce. But carnivorous plants use nectar to kill. Insects lands on a leaf expecting a meal . . . only to find it’s their last!

Over millions of years, the leaves of carnivorous plants transformed into many different types of amazing traps. The simplest is called a flypaper trap, where a plant’s leaves secrete a sticky mucus to trap bugs. Once prey steps on the leaves of a butterwort plant, it’s frozen in place. Then the plant injects special enzymes that digest the insect right where it got stuck.

Sundews also rely on mucus. They have tiny hairs called trichomes that stick out of their leaves. Each trichome has a drop of sweet—and sticky—mucus on its tip. As an insect struggles after getting stuck in the mucus, the trichomes are activated and pull the leaves inward. This wraps the leaves around the prey, making a bug burrito.

Pitcher plants use a different method. All 100 species have large leaves shaped like a jug with a lid-shaped leaf attached to its rim. Nectar covering the lid lures unsuspecting prey. Inside the jug is a mixture of water and enzymes that digest any creature that falls into it. The jug’s sides are slippery, making escape nearly impossible. Each species of pitcher plant has a unique shape. Sometimes, the size and shape of the pitchers on a single plant can vary!

The leaves of carnivorous plants have evolved into many different types of traps. The butterwort plant has the simplest type. It’s called a flypaper trap. It oozes a sticky mucus to trap bugs. Any prey that steps on the leaves gets stuck immediately. Then the plant releases chemicals that digest the insect right where it got stuck.

Plants called sundews also rely on mucus. They have tiny hairs that stick out of their leaves. Each hair has a drop of sweet and sticky mucus on its tip. Insects get stuck in the mucus. As they struggle to escape, the hairs curl up, which pulls the leaves inward.  They wrap around the prey like a bug burrito!

Pitcher plants use a different method. Their large leaves are shaped like a jug with a lid on top. Nectar on the lid lures unsuspecting insects. But the edge of the jug is slippery, and any prey that lands falls right in. Chemicals inside the jug digest the unfortunate insect. Each species of pitcher plant has a unique jug shape. Sometimes the same plant can have different sizes and shapes! 

Patrick Moldowan

Even salamanders can become a meal for a pitcher plant.

BEYOND BUGS

In the summer of 2017, student biologists made a surprising discovery in the jug of a pitcher plant in the bogs of the Algonquin Wildlife Research Station in Whitney, Canada. They found the gooey remains of a tiny salamander. Were these plants regularly snacking on salamanders? To find out, biologist Patrick Moldowan and his team monitored 144 plants. About 20 percent of them caught at least one salamander. It turns out that as these young salamanders emerge from the water, they sometimes fall into the plants’ traps.

“A salamander is a huge nutritional boom,” says Moldowan. An insect meal would be like eating a small salad, but a salamander is like a large steak dinner, he says.

In the summer of 2017, student biologists made a surprising discovery. They were studying pitcher plants in a bog in Whitney, Canada. They peered inside the jug of one pitcher plant. Inside were the gooey remains of a tiny salamander.

Were these plants regularly snacking on salamanders? Biologist Patrick Moldowan and his team decided to find out. They monitored 144 pitcher plants. About 20 percent of them caught at least one salamander. The young salamanders sometimes fall into the pitcher plants as they emerge from the water, the scientists found.

“A salamander is a huge nutritional boom,” says Moldowan. An insect meal would be like eating a small salad, he says. But a salamander is like a large steak dinner. 

Chien Lee/NPL/Minden Pictures

Shrew poop is the main source of nutrients for this pitcher plant in Borneo!

Salamanders aren’t the weirdest things to be found digesting in a pitcher plant. Back in 2009, scientists discovered a pitcher plant in the Philippines that preys on rats. The following year, a plant was found in Borneo that gets most of its nutrients from the poop of tree shrews!

As strange as they are, carnivorous plants are just one example of wild and wacky things we can find in nature. “There are so many things waiting to be discovered in your backyard,” says Moldowan.

Salamanders aren’t the weirdest thing scientists have found in a pitcher plant. Back in 2009, scientists discovered a pitcher plant in the Philippines that preys on rats. The following year, an even weirder plant was found in Borneo. It gets most of its nutrients from the poop of tree shrews!

Carnivorous plants are spectacularly strange. But they’re just one example of wild and wacky things we can find in nature, says Moldowan. “There are so many things waiting to be discovered in your backyard.” 

Use this information to calculate the volume of select pitcher plants. Use 3.14 for pi and round your answers to the nearest hundredth. Record your work and answers on our answer sheet.

Use this information to calculate the volume of select pitcher plants. Use 3.14 for pi and round your answers to the nearest hundredth. Record your work and answers on our answer sheet.

Like sundews, an N. albomarginata pitcher plant has trichomes on the rim of its jug that attract termites. Its pitcher is shaped like a cylinder with a radius of 1 centimeter and a height of 7.8 cm. What’s this pitcher plant’s approximate volume?

Like sundews, an N. albomarginata pitcher plant has trichomes on the rim of its jug that attract termites. Its pitcher is shaped like a cylinder with a radius of 1 centimeter and a height of 7.8 cm. What’s this pitcher plant’s approximate volume?

N. ampullaria has a small spherical jug. Not only do these plants eat insects, but they have also been found to break down leaves and bark that fall into the jug too. On average, this pitcher plant’s jug has a radius of about 2 cm. What’s it’s approximate volume?

N. ampullaria has a small spherical jug. Not only do these plants eat insects, but they have also been found to break down leaves and bark that fall into the jug too. On average, this pitcher plant’s jug has a radius of about 2 cm. What’s it’s approximate volume?

N. hemsleyana sometimes feeds on bat poop! It is cone-shaped, with a radius of 1.85 cm and a height of 18 cm. What’s its volume?

N. hemsleyana sometimes feeds on bat poop! It is cone-shaped, with a radius of 1.85 cm and a height of 18 cm. What’s its volume?

N. gracilis has wax crystals on its pitcher lid. When it rains, the crystals become slippery, and insects will slip into the jug. It’s cylinder-shaped with a radius of 0.8 cm and a height of 6.2 cm. What’s its volume?

N. gracilis has wax crystals on its pitcher lid. When it rains, the crystals become slippery, and insects will slip into the jug. It’s cylinder-shaped with a radius of 0.8 cm and a height of 6.2 cm. What’s its volume?

A. Many tropical pitcher plants are vines with several pitchers. Pitchers grow on the ground and also hang from branches in the air. Depending on the location, pitchers have different shapes. An N. bicalcarata pitcher on the ground is spherical with a radius of 3 cm. What’s its volume?

A. Many tropical pitcher plants are vines with several pitchers. Pitchers grow on the ground and also hang from branches in the air. Depending on the location, pitchers have different shapes. An N. bicalcarata pitcher on the ground is spherical with a radius of 3 cm. What’s its volume?

B. The N. bicalcarata pitchers that grow higher up are cylindrical with a radius of 2 cm and a height of 7.7 cm. What’s their volume?

B. The N. bicalcarata pitchers that grow higher up are cylindrical with a radius of 2 cm and a height of 7.7 cm. What’s their volume?

C. Which type has a greater volume and by how much?

C. Which type has a greater volume and by how much?

A. N. rafflesiana typica is found across Southeast Asia. An average pitcher on the ground is a cylinder with a radius of  2.1 cm and a height of 6.5 cm. What’s its volume?

A. N. rafflesiana typica is found across Southeast Asia. An average pitcher on the ground is a cylinder with a radius of  2.1 cm and a height of 6.5 cm. What’s its volume?

B. A hanging pitcher of N. rafflesiana typica is a cone with a radius of 2.3 cm and a height of 8 cm. What’s its volume?

B. A hanging pitcher of N. rafflesiana typica is a cone with a radius of 2.3 cm and a height of 8 cm. What’s its volume?

N. rafflesiana gigantea is an especially large subspecies found in Borneo. This plant’s lower pitchers are cylindrical, with a radius of 3.5 cm and a height of 12.9 cm. But the hanging pitchers are more cone-shaped, with a radius of 3.6 cm and a height of 22.5 cm. Which shape has a greater volume?

N. rafflesiana gigantea is an especially large subspecies found in Borneo. This plant’s lower pitchers are cylindrical, with a radius of 3.5 cm and a height of 12.9 cm. But the hanging pitchers are more cone-shaped, with a radius of 3.6 cm and a height of 22.5 cm. Which shape has a greater volume?

What do you notice about the differences between the volume and shape of the ground pitchers and the hanging pitchers?

What do you notice about the differences between the volume and shape of the ground pitchers and the hanging pitchers?

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