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Mutualism is a form of symbiosis in which both organisms benefit from the presence of the other. In this image, mutualism is shown through the honeybee pollinating the buttonbush flower. The bee collects nectar from the flower which is eventually turned into food for the colony. The pollen that adheres to the bee's fur is transferred to a female part of the plant as the bee travels, which allows the flower to produce the seeds that will propagate its species.
Pollen represents the male reproductive portion of a plant. More specifically, each pollen grain contains two sperm nuclei, which are transferred to the female part of a plant through various means of pollination. Pollen fertilizes the egg, producing a zygote that will eventually become a seed. Pollen producing anthers are a characteristic of angiosperms like the one shown here. In this image, dusty yellow pollen can be seen on the anthers of the wildflower.
An organism that exhibits bilateral symmetry has a physical appearance that forms a mirror image of itself over a single plane. Many animals have evolved to be bilaterally symmetrical because evenly balanced appendages allow for optimal mobility. The monarch butterfly seen here is an example of an organism with a bilaterally symmetrical body. The pattern and shape of each wing is an exact reflection of the other, as is the butterfly's body.
The cuticle layer of a plant is the hydrophobic outer layer that exists on all leaves and non-woody stems. A plant's cuticle layer acts as a shield to harmful external conditions. The structure prevents excess evaporation of water from the plant's surface and protects against contamination of the plant tissue from unsanitary water, dirt and various microorganisms. The leaves of the boxwood bush shown above have glossy cuticle layers that glare in the sun; in rainy conditions, water would bead up on the waxy cuticle surface.
The stamen is the male reproductive part of a flower. It is broken into two main parts, the filament, which functions as a stalk, and the anther, which is the pollen producing portion of the flower. In this image of a daylily, about six dark golden anthers can be seen in the center of the flower, supported by the lighter colored filaments.
The basic functions of plant stems are; support, transport and storage of water and nutrients, and the production of new tissues. A modified stem of a plant is any stem that serves a purpose outside of these standard characteristics, typically as an adaptation to an unconventional environment. Vines are an example of a modified stem that allow a plant to climb various surfaces and provide additional stability. In the image, the vines of a crossvine plant can be seen climbing a metal rod.
Autotrophs are organisms that produce their own food, hence their other name, producers. Typically, these organisms obtain their energy by synthesizing glucose through photosynthesis. When sunlight is not present however, certain autotrophs can use the energy of inorganic reactions to produce glucose, in a process known as chemosynthesis. Although autotrophs do not eat other organisms, they are consumed by heterotrophs, or consumers. An example of an autotroph that is eaten by consumers, even humans, is the rosemary plant seen above.
In general, a frond is any large divided leaf. The leaves of ferns and palm trees are primarily referred to as fronds, both scientifically and in common English. Fronds have strong center stems off of which small leaflets branch. This structure can be seen in the fern above. Each main branch is one frond, and its smaller triangular leaves are known as pinnae. The spores of ferns develop on the underside of its pinnae.
Phloem is a structure in vascular plants that transports sugars from the leaves, called "sources", to nonphotosynthetic parts of the plant, called "sinks". Sinks can be either roots, new shoots or developing seeds. The sugars are transported as a water-based sap and can move either up or down the channel to the nearest sink in a process called translocation. In the trunk of the oak tree seen above, a layer of living phloa is located in a ring just within the cork layer.
In vascular plants, xylem is the transport tissue that carries water and minerals from the roots to leaves and shoots. The channels also provide support for the plant and store water that is not yet needed. Unlike phloem, xylem can only carry its contents in an upward direction. Xyla take in water when a loss of moisture in the leaves via transpiration creates a negative pressure that draws water up from the soil. In the transvaal daisy seen here, the xyla run lengthwise along the inside of the stem.
A gametophyte is the plant, or phase in a plant's life cycle, that produces the gametes that will eventually form a zygote. Plants and some alga have a life cycle known as alternation of generations that is partially sexual and partially asexual. The gametophyte is the sexual phase of this cycle, producing the sperm and egg cells that will combine and eventually grow during the asexual phase of the cycle. The gametophyte phase is the dominant phase in most bryophytes, or mosses. In the image of moss, the gametophyte portion of the plant is the entire soft green covering.
The sporophyte is the asexual stage of the alternation of generations in plants and alga. The alternation of generations is the term used to describe a plant's life cycle because a plant alternates from a sexual phase to an asexual phase and back again. The sporophyte phase is the growth portion of the cycle and produces the sex organs that will lead to the commencement of the sexual phase. Sporophyte shoots can be seen arising as thin fibers from the green moss in the image.
Segmentation of an animal refers to the general repetition of parts. The main three phyla that exhibit segmented bodies are annelida, arthropoda, and chordata. Insects, belonging to the phylum arthropoda, have segments that are grouped into larger sections of the body known as the head, abdomen and thorax. On the dragonfly seen here, the abdomen is the slender tail-like structure and is divided into ten segments. The main part of the body that holds the wings is the thorax which consists of three segments. Finally, the head is the small round segment at the front end of the dragonfly.
The carpel is a part of the female reproductive organ of a flower and consists of the stigma and style. The style is a long stalk the supports the stigma. The stigma lies at the end of the carpel and collects pollen on fine hairs. Once on the stigma, pollen grains extend pollen tubes down the style, and the tubes deliver sperm cells to the ovary. In this image of a hibiscus, the style is the slender pink stalk extending from the center of the flower. The style of a hibiscus separates into what are called style branches; the burgundy colored stigmata attach to the end of each branch.
Endotherms, or warm-blooded animals, are capable of generating their own body heat independently from external temperatures. Endotherms can adjust their metabolic heat production in order to regulate their internal temperature; they have a greater number of mitochondria in their cells than ectotherms, which increases the amount of fats and sugars they can metabolize. The classification of endotherms consists of mammals and birds. The cat seen above, a mammal, is an example of an endotherm.
K-strategists, also known as k-selected species, are species whose populations remain relatively close to the carrying capacity of their environment. This is because k-strategists live in more stable conditions, therefore the size of their population is more dependent on density related factors. K-strategists birth in small numbers and are more attentive during the parental stages of development. Members of a k-selected species also tend to be large in size and live longer. Horses are an example of a k-strategist as they exhibit all of the qualities described above.
An exoskeleton is the external skeleton that forms a rigid outer covering for the bodies of arthropods and some other invertebrates. Exoskeletons are composed of chitin, a complex polysaccharide, and calcium carbonate. They contain flexible joints and an inner layer of muscles that allow for mobility of the animal. The image above shows the molted exoskeleton of a cicada. Exoskeletons do not grow with the animal, therefore they must be shed, allowing the animal to grow before its new exoskeleton hardens.
An r-strategist, or r-selected species, is a species that emphasizes growth rate as its means of survival. R-strategists are typically predominant in unstable environments because they are able to reproduce quickly and in large numbers. Members of an r-selected species have short life expectancies, take little time to mature and are relatively small in size. The cotton-tailed rabbit exhibits all of these qualities and can therefore be classified as an r-strategist.
A hermaphrodite is an organism that exhibits both male and female reproductive organs. Hermaphroditism is a characteristic common among fish and gastropods. Those known as sequential hermaphrodites are born a certain sex but can change into the opposite sex either one or multiple times, depending on the species. The earthworm seen here is an example of a simultaneous hermaphrodite, which has both male and female reproductive parts for its entire life. Because they produce both sperm and eggs at the same time, simultaneous hermaphrodites have the ability to mate with any other member of their species and some can even self-fertilize.
Gymnosperms and angiosperms together make up the spermatophytes, or seeding plants. However, gymnosperms differ from angiosperms because of their characteristic exposed seeds. The leaves of a gymnosperm are generally needles that remain green year-round. Gymnospermous plants are taxonomized into four categories; coniferophyta, gnetophyta, ginkgophyta, and cycadophyta. The sago palm seen here belongs to the group cycadophyta, which typically exhibit stout woody trunks and heads of thin brittle leaves.
Spores allow for asexual propagation of a species because, unlike gametes, spores contain both male and female reproductive parts. Reproduction begins when a dry surrounding atmosphere increases pressure within the plant, causing spores to emerge on the plant's exterior. These spores are then spread by animals, wind or water and once relocated will begin the growth of a new plant. A fern's spores are small rust colored dots that develop on the underside of its fronds. While hard to see at first, the spores on this fern can be seen in the upper left corner of the image.
A lichen is an example of a symbiotic relationship wherein a fungus and a photosynthetic organism, usually green algae or cyanobacteria, coexist and benefit from the other. The fungus receives a food supply from the photosynthesizer which in turn receives the water and nutrients absorbed by the fungus. Three different types of lichen can be seen on the chair above -- crustose, foliose and fruticose. The characteristics of these variations are; flat orange, thin leaf-like white and three-dimensional bristle-like, respectively.
An ectotherm is an animal whose body temperature is regulated by its surroundings rather than being generated internally, otherwise known as a "cold-blooded animal". To do this, ectotherms can use the heat of the sun, a heated rock, or the water it inhabits in the case of fish. The primary ectotherms include; amphibians, reptiles, fish and invertebrates. The adolescent garden snake seen hiding in the photograph is an example of an ectotherm.
When a plant has modified leaves, it is using its leaves for a purpose other than photosynthesis. The example shown above is of a pitcher plant, a carnivorous plant whose tube shaped leaves have slick, grooved inner walls that trap insects and cause them to drown in a digestive fluid. The minerals obtained from the dissolved insects provide the pitcher plant with its nutrition.
CAM stands for crassulacean acid metabolism and is a feature of plants that have adapted to survive in arid environments. CAM plants minimize photorespiration by only opening their stomata at night to collect carbon dioxide, thus preventing excess evapotranspiration from occurring during the day. The prickly pear cactus seen here exhibits this behavior as it stores carbon dioxide in vacuoles at night then releases it in the morning where it takes part in the Calvin cycle.
