Carnivorous Plants Essay Research Paper Carnivorous PlantsIn

Carnivorous Plants Essay, Research Paper

Carnivorous Plants

In a world where plants are at the bottom of the food-chain, some

individual plant species have evolved ways to reverse the order we expect to

find in nature. These insectivorous plants, as they are sometimes called, are

the predators , rather than the passive prey. Adaptions such as odiferous lures

and trapping mechanisms have made it possible for these photosynthesizers to

capture, chemically break-down and digest insect prey (and in some cases even

small animals.) There is no reason to fear them though. The majority are

herbaceous perennials, usually only 4 to 6 inches high, and nothing like the

plant in “Little Shop of Horrors”.

Almost all carnivorous plants have a basically similar ecology and

several different species are often found growing almost side by side. They are

most likely to be found in swamps, bogs, damp heaths and muddy or sandy shores.

Drosophyllum lusitanicum from Portugal and Morocco is the one exception, it

grows on dry gravelly hills. Like other green plants, carnivorous plants

contain the organic pigment chlorophyll. This pigment helps to mediate a

chemical process called photosynthesis. This converts light energy into the

chemical bond energy of carbohydrate which is utilized as cellular energy, plant

growth and development. Water, carbon dioxide, nutrients and minerals are also

needed for survival. In wetlands, where stagnate water contains acidic

compounds and chemicals from decaying organic matter many plants have a

difficult time obtaining necessary nutrients. It is in these nutrient poor

conditions that some plants evolved different ways of obtaining nutrients. The

ability of carnivorous plants to digest nitrogen -rich animal protein enables

these plants to survive in somewhat hostile environments.

The evolution of carnivorous plants is speculative due to the paucity of

the fossil record. It is believed that plant carnivory may have evolved millions

of years ago from plants whose leaves formed depressions that retained rain

water. Small insects would sometimes fall into these water reservoirs and drown,

eventually being decomposed by bacteria in the water. The nutrients from the

insects would be absorbed by the leaf. The deeper the leaf depression the more

insects that could be drowned. This would have created a distinct survival

advantage allowing some plants to better compete in nutrient poor soil. As time

passed, these plants would evolve more effective trapping mechanisms.

There are more than 500 known species of carnivorous plant, although

some are now extinct. Classification is done using the standard binomal system

and is based primarily on the floral characteristics of the plants, not the

trapping mechanisms. They are divided into two groups based on corolla

structure; Choripetalae and Sympetalae. The group of plants categorized as

carnivorous belong to seven families, which are recognized by the suffix .aceae’,

and fifteen genera. More than half of the species belong to the family

Lentibulariacene that is marked by bilaterally symmetrical flowers with fused

petals. The remainder of the species belong to six families marked by radially

symmetrical flowers with separate petals. Classification is illustrated in the

chart below in addition to the geographic range, the number of species, and the

type of trapping mechanism.

Family Genus species Geographic

Distribution Type of Trap Byblidaceae Byblis

2 Australia Passive flypaper

Cephalotaceae Cephalotus 1 S.W.

Australia Passive pitfall Dioncophyllaceae

Triphyophyllum1 West Africa Passive flypaper

Droseraceae Aldrovanda 1 Europe, Asia,

Africa, Australia Active

Dionaea1 North & South Carolina

Active steel Family Genus # of species

Geographic Distribution Type of Trap

Drosera 120 Omnipresent Passive

flypaper

Drosophyllum1 Morocco, Portugal, Spain

Passive flypaper NepenthaceaeNepenthes 71

East Indies Passive pitfall Sarraceniaceae

Darlingtonia1 California & Oregon, Passive

pitfall

Western Canada

Heliamphora6 North and South

America Passive pitfall

Sarracenia9 North America

Passive pitfall LentibulariaceaeGenlisea 14

Tropical Africa and Passive lobster

South America,

Madagascar

Pinguicula 50 Northern

Hemisphere and Passive pitfall

South America

Polypompholyx2 Australia

Active mousetrap

Ultricularia 300 Omnipresent

Active mousetrap

In the above chart, it can be seen that there is a large number of

different types of traps. The modified leaf traps of carnivorous plant can each

can be categorized as either active or passive. An active trap is one that

employs rapid movement as an integral part of the trapping mechanism, a passive