The Study of Life: Characteristics, Classification & Organization
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This document provides an overview of the key characteristics of life, including organization, acquiring materials and energy, reproduction, response to stimuli, homeostasis, growth and development, and adaptation. It also discusses the classification of living things into domains, kingdoms, and species. Finally, it covers the organization of the biosphere into populations, communities, ecosystems, and the human impact on biodiversity.
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- The diversity of life is astonishing. There are approximately 2 million species described so far, scientists believe that there may be as many as 5-30 million species. Life exists almost everywhere on the planet Earth.
- All living things have certain characteristics in common. All living things are Organized Acquire materials and energy Reproduce Respond to stimuli Are homeostatic Grow and develop Have the capacity to adapt
- Living things can be organized in a hierarchy of levels. At the lowest level of organization, atoms join to form the molecules (including DNA) that are found in cells. Cells, the smallest units of life, differ in size, shape, and function. Tissues are groups of cells tat serve the same function. Organs, which are composed of different tissues, make up the organ systems of complex organisms. Each organ and organ system performs functions that keep the organism alive and well.
- Living things cannot maintain their organization or carry on life ’s other activities without outside sources of nutrients and energy. Food provides nutrients and energy for organisms Energy is the capacity to do work.
- Life comes from life (biogenesis). For some time people believed in spontaneous generation which was the belief that life could arise from arise from non-living or decomposing matter. Work done by scientists since the late 1600 ’s demonstrated that organisms reproduce to make more of themselves. DNA (and RNA for some cases) is the genetic material that allows organisms to reproduce. DNA contains hereditary information that directs the structure and metabolism of a cell.
- Living things have the ability to respond to internal or external stimuli. Those stimuli could be such things as food sources. Organisms use different mechanisms to respond; animals are dependent upon their nervous and musculoskeletal systems to move. Other organisms can move in response to stimuli as well. An example is a plant moving toward sunlight. Living things also demonstrate homeostasis. Homeostasis literally means “staying the same.” Homeostasis exists when the organisms internal environment remains relatively constant despite fluctuations in its external environment. Organisms work to maintain homeostasis. GIVE EXAMPLE OF TEMP REGULATION IN HUMANS
- Living things grow and develop. Growth refers to an increase in the size of an organism and often in the number of cells. Development refers to all the changes that take place between conception and death. (increase in complexity)
- Living things have the capacity to adapt Throughout the ~4 billion years that life has existed some individuals of species have possessed characteristics that made them better suited to survive, Those characteristics are known as adaptations. Those adaptations allow those individuals to live longer and produce more offspring. This differential reproductive success results in changes in the characteristics of the population. This process is known as natural selection. The change in the frequency of traits in populations and species is known as evolution.
- Living organisms are assigned to groups based upon their similarities. Classifying organisms began about 250 yrs ago with a gentleman by the name of Carl von Linne (also known as Linnaeus) who was a swedish botanist. Linnaeus realized early on that a system for recognizing and defining the properties of living beings would prevent chaos in scientific studies by providing each organism with a unique name and an exact “slot” in which to catalog it. This classification would serve as a means for future identification of that same organism and workers in many biological fields to know if they were discussing the same organism. The discipline of identifying and classifying organisms is known as systematics.
- The main units of a classification scheme are organized into several descending ranks, beginning with the most general all inclusive taxanomic group to the most specific Domains are the largest classification category. Biologists assign organisms to one of three domains based on biochemical and genetic evidence. Based on the current biochemical and genetic evidence 3 domains are currently described Archaea Bacteria Eukarya
- Archaea are single celled prokaryotes that lack a membrane-bound nucleus. Archae are found residing in environments that are often considered to harsh for other organisms to exist. Those environments include aquatic environments lacking oxygen; environments that are too salty, too hot, or too acidic for other organisms.
- Bacteria are also single celled organisms that lack a membrane-bound nucleus Bacteria can be found residing almost everywhere in water, soil, and atmosphere, as well as on/in the bodies of plants and animals. Most bacteria are harmless or beneficial; some however are pathogenic and may cause disease.
- Eukarya may be single celled or multicellular organsims that share the characteristic of having a membrane-bound nucleus. The domain Eukarya is divided further into 4 kingdoms Protists – range from unicellular to a few multicellular organisms (algae, water molds, etc) Fungi – molds, yeasts, and mushrooms Plantae – known as multicellular photosynthesizers; mosses, ferns, non-woody and woody flowering plants Anamalia – multicellular; invertebrates, fishes, reptiles, amphibians, birds and mammals
- Other categories include phylum, class, order, family, genus, and species. As we move from domain to species the groups become more specific. Let ’s compare the taxanomic breakdowns of a human and a protozoan. Humans and protozoa are both organisms with nucleated cells but placed in different kingdoms. Humans are multicellular animals (Kingdom Animalia) whereas protozoans are single-cellular organisms, that together with algae, belong to the Kingdom Protista. Of the several phyla humans belong to the phylum chordata. DOMAIN EUKARYA: cells with nuclei KINGDOM ANAMALIA: multicellular, motile, ingestion of food PHYLUM CHORDATA: dorsal supporting rod and nerve cord CLASS MAMMALIA: hair, mammary glands ORDER PRIMATES: Adapted to walk erect FAMILY HOMINIDAE: Adapted to walk erect GENUS HOMO: large brain, tool use SPECIES HOMO SAPIENS: Body proportions of modern humans SYSTEMATICS IS DYNAMIC. AS WE GAIN ADDITIONAL KNOWLEDGE AND FIND NEW WAYS OF CLASSIFYING THE GROUPS MAY CHANGE.
- Within the field of systematics is taxonomy (the assignment of a binomial, or two part name to each species) Many organisms are known by a common name, often suggested by certain dominant features. Common names are problamatic for science because they may vary from region to region. Scientific names provide a universal language to enable scientists from all over the world to communicate and exchange information with less confusion. Binomial names consist of a genus name which is the first name and a species name which is the second name. The genus name is always capitalized and both are always shown in italics. If they cannot be shown in italics they should be underlined.
- The biosphere is the zone of air, land, and water at the surface of the Earth where life is found. Populations refer to groups of individuals of a species in a given area. All of the different populations of species that interact within an area make up a community. An ecosystem encompasses all of the interactions of the community along with its physical habitat.
- The image depicts a grassland ecosystem Ecosystems are characterized by chemical cycling and energy flow. In an ecosystem, chemical cycling and energy flow begin when plants use solar energy and inorganic nutrients to produce food for themselves directly or indirectly for all other populations in the ecosystem. As one population feeds on another, chemicals and energy are passed along a food chain. With each transfer, some energy is lost as heat. Eventually all the energy dissipates as heat but the nutrients do not. After organisms die and decompose inorganic nutrients are returned to the environment and eventually may be reused by plants Climate largely determines where different ecosystems are located. The two most diverse ecosystems are tropical rainforests and coral reefs
- Humans modify existing ecosystems for our own purposes. We rely on healthy ecosystems for our own survival. But our actions have caused many ecosystems to be totally altered and are putting stress on most others. Our coral reefs and tropical rainforests which are millions of years old are quickly starting to disappear as a result of our actions. Preservation of our ecosystems are important to ensure our continued existence.
- The present biodiversity has been estimated to be as high as 5-30 million species. So far fewer than 2 million have been identified and named. It is estimated that the Earth is losing as many as 400 species per day due to human activities. Many biologist believe that the primary bioethical issue is that of the conservation of biodiversity.
- There are many scientists who study topics/subjects that seem very distant from everyday lives Some however study topics that are aimed at developing a technique or producing a product that will affect our everyday lives. Such work is referred to as technology.