25. Modified Stem of Plant

This is a picture of a thistle stem, which can be considered a modified stem of a plant. A stem acts as the central support means for a plant, and also the place where capillary action takes place. In the case of this thistle, the stem is modified to also act as defense with it's many thorns. In this way the thistle is a good example of a modified stem.

24. Modified root of plant

This is a picture of Bald Cypress "knees", a modified root of a plant. Roots typically provide soil nutrients and support to plants. In the case of the Bald Cypress, which typically lives in southern swamps, the roots are often completely submerged. This inhibits gas exchange. The Bald Cypress has adapted skyward-shooting "knees" to allow for gas exchange. In this way, the Bald Cypress is a good example of a modified root.

23. Cambium

This image shows the cambium of a tree. The cambium is the extremely thin living layer on a plant, between the xylem and phloem. This picture illustrates the cambium well because it shows where the cambium is, between the dark xylem and light phloem.

22. Phloem

This image shows the Phloem layer of a tree. The phloem is the part of the tree where sugars and other products are transferred from the leaves down the tree. The Red Oak pictured here is especially good at illustrating this function, as it has large, visible straws in its phloem.

 In the timber industry, it is commonly said that you can not make a barrel out of red oak, as it will leak, as a result of the large tubes in its phloem.

21. Xylem

This image shows the Xylem of a tree. The Xylem is the portion of a plant where water and nutrients are conducted upward from the roots. On a tree, it is often referred to as the bark. This picture illustrates the xylem well because it shows the contrast in color between the dark xylem and light phloem, which it surrounds.

20. Heterotrophy

19. Autotroph

This is a picture of a tree, an autotroph. An autotroph is an organism that is capable of creating its own food, through chemo- or photo-synthesis.  This tree is a good example of an autotroph because it is shown here catching sunlight in its leaves so it can use photosynthesis to make glucose.

18. Frond

This is a picture of a Frond. A frond is a type of leaf that is lobed and divided intricately, and mainly found on ferns, cycads, and palms. This frond is a good example of a frond because it is compound and on a Japanese Painted Fern, one of the frond-producing plants.

17. Littoral zone organism

This is a picture of Cattails, a littoral zone organism. The littoral zone is the area of a lentic (stillwater) system where the photic zone meets the bottom. This is near the shore. Cattails are a good example of a littoral organism because they only live in shallow, standing water, such as that found in the littoral zone of most waterbodies.

16. Keystone Species

This is a picture of a beaver dam. A beaver dam shows how a beaver acts as a keystone species. A keystone species is a species on which an ecosystem depends on significantly. A beaver is an keystone species because it turns a stream ecosystem into what is known as a "beaver pond" - a marsh ecosystem - by building a dam. If the beaver were to disappear (the keystone species removed), the dam and marsh ecosystem would collapse. In this way a beaver is an "ecosystem engineer", a special type of keystone species.

15. Epithelial Tissue

This is a picture of human skin, or epithelial tissue. Epithelial tissue is the covering of the body parts. It can be exterior (skin) or interior (lining digestive tract and others). This picture demonstrates epithelial tissue well because it shows the structure of the outer surface of my epithelial tissue.

14. Hermaphrodite

This is a picture of a Nightcrawler. A hermaphrodite is an organism which possesses both male and female sex organs. All earthworms are hermaphrodites, and all nightcrawlers are earthworms. Therefore this nightcrawler makes a good example as a hermaphrodite.

13. K-strategist

The humans pictured are an example of a K-strategist. A K-strategist is one who produces few, high-energy investment offspring, with the expectation those few will survive and reproduce. The humans pictured are a good example because they spend 18 years before fledging. Humans spend high-energy on their few offspring.

12. r-strategist

This is a picture of a bluegill sunfish, an r-strategist. An r-strategist is an animal which produces many low-value offspring, most of which will not survive. The bluegill pictured is a good example of an r-strategist because it produces hundreds of thousands of offspring per female, most of which are consumed or perish in other ways before reproduction. It abandons its offspring soon after spawning, making them a low-energy investment.

11. Vestigial Structure

This is a picture of body hair, a vestigial structure in humans. A vestigial structure is a structure that is no longer necessary for survival in an organism, but persists because of a previous necessity on the evolutionary tree. Body hair on humans is a good example of this, because this hair does not perform the function of insulation and camouflage it performed on our ancestors.

10. Lichen

This is a picture of a Lichen. A lichen is an organism made up of algae and fungus. This is a good example of a lichen because it shows both the branching fungus and the green of the algae. This photo was taken in the Rocky Mountains of Montana, where clean air allows delicate symbiotic lichens to thrive.