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Characteristics of living organisms
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Characteristics of Living Things


  1. Identify the characteristics of living things.

    1. Living things are highly organized, from the smallest part to the largest.

    On the chemical level: atoms make up elements. Each element has a specific number of electrons that orbit the nucleus. In the center of the element, the nucleus has protons and neutrons. The number of protons in an element is always equal to the number the electrons. The number of neutrons may vary to make isotopes of that element. Elements come together to give up, accept or equally share electrons to make molecules.

    The smallest part of an organism is a cell.

    Some single-celled organisms are free-living and contain structures, called organelles, that allow them to be self-sufficient.

    More complex organisms are multicellular. In the case of a human, cells are organized into tissues. These have a common function like a muscle.

    Tissues are organized into organs like the heart.

    Organs are organized into organ systems, like the cardiovascular system. Organ systems functioning together make up a living organism.

    A population is an organization of more than one individual. This is generally all of one species in a particular area. We could talk about the population of squirrels in our area or dogs or cats.

    Enlarging our view, next comes a community. An example of a community is the town or place we live. A more accurate biological description would include all the living things in that area. A community is composed of many species, including plants and animals

    An ecosystem not only considers the living things in an area, but also the physical environment and the interrelated flow of energy. You may live in a desert ecosystem, a forest ecosystem, or another kind of ecosystem.

    Most complex of all is the biosphere. In our case, this includes the all the areas of our planet where living things are found.

    2. All living things have an ability to acquire materials and energy.

    Most of us call this eating! Then we have to be able to convert our food, a form of energy, to chemicals our cells can use through metabolism. Some organisms like plants, algae, and some microorganisms are autotrophs. The autotrophs we are most familiar with are the green plants that use photosynthesis to make their own "food." Some bacteria use chemosynthesis for their energy source. Animals and fungi are heterotrophs and capture their food in a variety of ways.

    The ability to acquire and use energy is extremely important. Without a constant input of usable energy, organisms would quickly become "disorganized" and die.

    In order to survive, organisms must be able to achieve homeostasis. Each type of organism has a specialized way to stay in balance with its outside and inside environments. A paramecium has a contractile vacuole that pumps excess water out of its cell in order to survive in a fresh water environment. You and I have an internal "thermostat" that helps us maintain a body temperature of about 98.6 degrees Fahrenheit.

    3. All living things have an ability to respond to their environment.

    This often results in movement of the individual toward safety. This helps to ensure survival of the organism. For example, as young children we learned to avoid hot stoves and busy streets.

    Plants also have some limited ability to move. They grow up toward the sun, and some have leaves able to turn to follow the sun, allowing them to photosynthesize better. Their roots grow down to search for water and minerals. If a plant doesn't get enough sunlight, water or minerals it will die.

    4. All living things have an ability to reproduce.

    All living things, even the smallest bacteria, have a chromosome containing DNA. Prokaryotes like bacteria only have one circular chromosome, called a plasmid. Eukaryotes, multicellular organisms like plants and humans, have a species-specific number of chromosomes. As humans, we have 46 chromosomes, in 23 pairs. Genes on chromosomes contain the instructions for the organism's structure and function.

    However, the amazing diversity of organisms on earth have resulted because most organisms reproduce sexually. Some, like earthworms are hermaphrodites. Most others have separate sexes, male and female, like marijuana plants, fish, birds, cattle and humans.

    In order for two organisms to combine their genetic information without doubling the number of chromosomes given to offspring, Mother Nature came up with a way to reduce the number of chromosomes. Without it, each new generation would have double the number of its parents' chromosomes. This halving is done by meiosis in the sex organs. In the female, the ovary produces haploid eggs and in the male the testes produces haploid sperm. Each of these gametes contains only one chromosome from each of the pairs of chromosomes.

    During fertilization, the sperm and egg unite to form a zygote, a diploid individual. This new individual is different from either parent, although it contains characteristics from both. This is what gives us the great diversity of life. In living things, we call this genetic biodiversity.

    5. All living things have an ability to adapt.

    Modifications enable an organism to survive in its environment. Natural selection allows individuals with better adaptations to survive better and reproduce more. Thus, their characteristics are passed into future generations and that makes the species stronger. However, it is important to note that individuals can only adapt to their environment, and species don’t adapt, they evolve.

    All living things:

    1. Are comprised of one or more units called cells

    2. Reproduce (sexually or asexually)

    3. Grow and develop

    4. Obtain and use energy

    5. Respond to their environment

    1) All living things are comprised of cells.

    Cell- a collection of living matter enclosed by a barrier that protects it from its surroundings.

    Unicellular organism- a one-celled organism (e.g. bacteria)

    Multicellular organism-

    an organism made of more

    than one cell, starfish, turtle)

    2) All living things reproduce

    …that is, they produce new individuals similar to themselves. Why is reproduction necessary?

    To replace the dead ones.

    Two Kinds of Reproduction:

    Asexual Reproduction:

    The prefix a- means without, so without sex.

    A single organism reproduces without the aid of another.

    - Common among bacteria and other microscopic organisms

    - Splitting (bacterial cells) or budding (plants)

    Sexual Reproduction:

    two cells from different individuals unite to produce the first cell of a new organism.

    Union of a sperm cell

    from male united with

    egg cell from female.

    * Some organisms are capable of sexual and asexual reproduction.

    3) All living things grow and develop

    Life does not necessarily mean continuous growth

    During growth organisms undergo a cycle of changes called development.

    Bodily maintenance occurs throughout life (requires energy). Aging occurs when an organism loses its ability to maintain itself.

    4) All living things obtain and use energy Energy required for growth and maintenance

    Energy (usually sugars) obtained from the environment

    Anabolism - a process (such as tissue growth) that involves synthesizing, or putting together, complex substances from simpler substances (sugars) (REQUIRES ENERGY)

    Catabolism- final breakdown (digestion) of complex substances into simpler ones, (RELEASES ENERGY)

    Metabolism- total sum of all chemical reactions in the body, or the balance between anabolism and catabolism

    5) All living things respond to their environment Stimulus (plural stimuli)- anything that causes an organism to react

    Irritability- the ability to react

    Can plants respond to stimuli? Yes, but normally not as quickly as animals.

    Homeostasis- (homeo- similar, -stasis standing) an organism’s ability to maintain the constant or stable conditions necessary for life.

    Just as the thermostat automatically cools or warms a room if it deviates from a desired temperature, your body maintains a constant temperature, 98.6 F or 37 C, at which it functions optimally.

    1) Living things are highly ordered.

    2) Living things are organized into units called cells.

    3) Living things use energy from their environment

    4) Living organisms respond to stimuli -

    5) Living things develop.

    6) Living things reproduce themselves

    7) Living things contain genetic information