25. Tropism

This is a picture of a sunflower. This is an example of tropism. Tropism is the turning of a part of an organism or an organism itself in response to external stimulus. For examples. sunflowers respond to the sun, an external stimulus, and turn towards it. Different plants and animal respond to different external stimuli; therefore, there are different types of tropisms like hydrotropism, phototropism, etc. 

24. Pollen

This is a picture of a flower. A flower has pollen. In the picture the pollen is the yellow powder located in the middle of the flower. Pollen is a powdery substance, usually yellow in color, that consists of microscopic grains, that contain gametes, from the male part of a flower. Since the grains contain gametes pollen that's transported by wind, insects, and other animals can fertilize the female ovule. Pollen is also a source of many allergies in the spring time.

23. Radial Symmetry (animal)

This is a picture of a starfish. This is an example of radial symmetry. Radial symmetry occurs when an organism can be divided equally about a central point kind of like a pizza cut into equal parts. The symmetry can be divided any number of planes. If the starfish was cut using a four piece plane then all the cut pieces would be equal. Other examples of organisms with radial symmetry include: jellyfish, sea urchins, coral polyp. etc. 

22. r Strategist

This is a picture of fish. Fish are r strategists. R strategists, also referred to as r-selected species, are species whose populations are controlled by their biotic potential. When compared to a K-strategist r strategists have a short life, rapid growth, early maturity, many small offspring, and little parental care or protection. R-selected species tend to be smaller than K-selected species. Examples of r strategists include: fish, mice, oysters,etc.

21. Population

This is a picture of people. The people in the picture are an example of a population. Population is all the organisms of the same group or species that live in a specific geographical area and are able to breed. The picture is of a group of the same species, human, that are able to interbreed, and in the geographical area of Yorktown, VA.

20. Pollinator

This is a picture of a bee, on a flower, pollinating. The bee is an example of a pollinator. A pollinator is an agent that transfers pollen from the anther of a flower to the stigma of a flower. There are many differents kinds of pollinators such as bee, birds, insects, etc. This relationship between the bee and the flower is also an example of mutualism because both the flower and bee benefit. 

19. Mutualism

This is a picture of a clownfish in as sea anemone. This is an example of a symbiosis relationship that is mutualistic. Mutualism is where both the clownfish and sea anemone benefit and are able to flourish through symbiosis. The clownfish, which is territorial, protects the sea anemone from other marine predators and in return the sea anemone provides the clownfish with a home. The clownfish is the only fish that does not get stung by the tentacles of the sea anemone. Another example of mutualism is the symbiotic relationship between a flower and a bee.