Catalog Number:
401270
Specimen Count:
2
Collector:
N. Erwin
Locality:
US Mid Atlantic (PA, NJ, MD, DE, DC, VA, WV)
Collecting Date:
19 May 2013
Collecting Locality:
North America, United States, Virginia, Fairfax County
Upper Level Taxonomy:
Plantae, Equisetopsida, Magnoliidae, Lilianae, Poales, Poaceae, Pooideae

Flowering plants are the most diverse and recent group of land plants, with ancestors dating back 130 million years. In part, they owe their diversity of more than 300,000 species to the evolution of flowers and fruits. Because they reproduce sexually, flowering plants make female and male sex cells. A flower is a fancy container for sex cells, and a fruit is a fancy container for seeds (after fertilization). Many flowers attract animal pollinators by giving nectar rewards. When a pollinator travels from flower to flower in search of nectar, it transfers pollen, enabling sexual reproduction of the plants. Flowering plants often have specific features such as flower shape and color to attract pollinators. Bright blue flowers tend to attract bees, yellows attract butterflies, and reds attract hummingbirds. Flowers pollinated at night by moths and bats are usually white with strong scents. Natural selection for showy flowers with sweet nectar has acted in tandem with natural selection for capable pollinators for millions of years in a process called coevolution. Flowering plants also owe their success to coevolution for dispersal of their seeds enclosed in fruits. For example fleshy fruits have evolved to attract humans and other animals that will eat them and drop the unharmed seeds elsewhere.

Monocots begin their lives nourished by a single seed leaf (cotyledon). The leaf provides nutrients to the developing seed until it grows its first true leaves that can photosynthesize to make food. The true leaves are larger with parallel veins running from stem to tip. Monocots are herbaceous plants that typically don't grow large, but they are economically significant. Grasses are monocots that dominate grassland ecosystems such as prairies, and they are the source of grains such as rice, wheat, and corn that provide most of the world's food. Some monocots grow into trees sturdy enough to supply building materials, such as bamboo and palms. Many important tropical fruits, including bananas, coconuts, and pineapples, are from monocots. Some monocots in seasonal climates have evolved underground food storage organs such as bulbs to survive cold or dry conditions. The first flowers to bloom in the spring, such as daffodils and crocuses, are monocots from bulbs or bulb-like corms. Orchids are the most diverse group of monocots with over 22,000 species that are known for their beautiful flowers and relationships with insect pollinators.

In plants, the evolution of special systems to transport fluids through their bodies (vascular systems) was a successful innovation that allowed them to conquer the land. Vascular systems allowed plants to grow large and colonize a wide range of habitats from the artic to deserts and rainforests. Today, most plants we see are vascular, with cells organized into tissues specialized for transporting nutrients and fluids. These vascular tissues include xylem, which takes water and nutrients from roots to the rest of the plant. Working xylem cells are dead, just hollow tubes bounded by cell walls. Another important tissue, phloem, takes sugars (made by photosynthesis) from the leaves to the rest of the plant. Vascular plants also have advanced systems for other functions, such as support, protection, and photosynthesis. For example, leaves are a thin but complex sandwich consisting of upper layer that secretes protective wax, middle layer packed with photosynthesizing cells, and lower layer with pores (stomata) for exchanging gases.

Without plants, we could not survive and there would not be much diversity of life on Earth, just some tiny bacteria, algae, fungi, and tiny ocean organisms. Because of their ability to make their own food, plants are at the base of nearly every ecosystem food web. The secret of success for plants is a light-absorbing molecule (a pigment) called chlorophyll that captures the energy of sunlight by electron movements. This energy is used to make sugars from carbon dioxide and water. The leaves of plants are powerhouses for sugar manufacturing, packed with cells that contain chlorophyll. Plants uptake carbon dioxide for photosynthesis, and they release oxygen as a “waste” product, thereby supplying our atmospheric oxygen. Plants are essential for keeping carbon dioxide out of the atmosphere that would otherwise contribute to global warming. In addition plants are directly or indirectly provide the food we eat.

While most animals move around during some part of their life cycle, plants are stationary. Their roots are typically underground, anchoring the plant to one spot. An organism that lives in one spot must find ways to meet its needs, such as for food and reproduction, without moving around. Plants are able to make their own food (by photosynthesis), as long as they have sunlight and water. Roots usually take care of the water need, extending downward to tap underground sources. As for light, having many leaves increases the surface area exposed to the sun. Plants also can capture more light by growing towards it either by getting taller or bending. Plants have evolved many ways to reproduce and spread without moving: natural cloning through vegetative shoots; attraction of pollinators to unite pollen with eggs; and seeds that are adapted for dispersal by wind, water, or animals.