Cell biologists consider questions such as metabolism and other questions about structure and function within and between cells. Tissue is made of cells that work together to perform a certain task.
The Levels of Organization
Muscle tissue, connective tissue, and neural tissue are some types of tissue. Histologists are an example of biologists who work at this level. Examples of organs are the brain, heart and lungs. Anatomy is an example of a biology specialty concerned with this level. An organ system is a group of organs that work together to perform specific bodily functions.
The respiratory system, for example, uses the lungs, airways and respiratory muscles to inhale oxygen and release carbon dioxide in animals. Physiologists study the function of parts of the body as they work together.
Though physiologists can work at any level of biological organization, they often answer questions related to organ systems. An organism is a recognizable, self-contained individual.
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- From Chemical to Biological Organization?
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Organisms can be unicellular organisms such as bacteria or amoebae, or multi-cellular organisms comprised of organs and organ systems. A human being is an example of a multi-cellular organism.
Protometabolic pathways: exploring the chemical roots of systems biology
A population is a group of multiple organisms of the same species within a specific area. For example, a pride of lions in Kenya, Africa, is a population.
A community consists of all the different species within a certain area. The population of lions in Kenya, plus the populations of gazelles, giraffes, elephants, dung beetles, and all other species in that area, add up to a community. An ecosystem is made up of all the communities in a certain area, as well as all the non-living, physical components of the environment. Mitochondria produce energy to power the cell while chloroplasts enable green plants to utilize the energy in sunlight to make sugars. All living things are made of cells, and the cell itself is the smallest fundamental unit of structure and function in living organisms.
This requirement is why viruses are not considered living: they are not made of cells. To make new viruses, they have to invade and hijack the reproductive mechanism of a living cell; only then can they obtain the materials they need to reproduce. Some organisms consist of a single cell and others are multicellular. Cells are classified as prokaryotic or eukaryotic. Prokaryotes are single-celled or colonial organisms that do not have membrane-bound nuclei; in contrast, the cells of eukaryotes do have membrane-bound organelles and a membrane-bound nucleus.
In larger organisms, cells combine to make tissues, which are groups of similar cells carrying out similar or related functions. Organs are collections of tissues grouped together performing a common function. Organs are present not only in animals but also in plants. An organ system is a higher level of organization that consists of functionally related organs.
Mammals have many organ systems. For instance, the circulatory system transports blood through the body and to and from the lungs; it includes organs such as the heart and blood vessels.
From Chemical to Biological Organization
Furthermore, organisms are individual living entities. For example, each tree in a forest is an organism. Single-celled prokaryotes and single-celled eukaryotes are also considered organisms and are typically referred to as microorganisms. All the individuals of a species living within a specific area are collectively called a population. For example, a forest may include many pine trees. All of these pine trees represent the population of pine trees in this forest.
Biological organisation - Wikipedia
Different populations may live in the same specific area. For example, the forest with the pine trees includes populations of flowering plants and also insects and microbial populations. A community is the sum of populations inhabiting a particular area. The forest itself is an ecosystem.