Biology & The Scientific Method

Biology & The Scientific Method

DNA Deoxyribonucleic Acid Composition A nucleic acid

made up of monomers nucleotides Recall: Nucleotides are made of

A phosphate group A nitrogenous base A 5-carbon sugar deoxyribose 4 Different Nitrogenous

bases Make Up DNA Adenine A Cytosine C Guanine G Thymine T Forming the Double Helix Composed

of sugar-phosphate strands ( two of them) Strands are held together by hydrogen bonds Base-Pairing hydrogen bonds could

create a nearly perfect fit between nitrogenous bases along the center of the molecule. This fit between AT and GC nucleotides is known as base pairing.

DNA Replication Process through which DNA is copied or duplicated This happens during the Synthesis Phase (S phase)

of the cell cycle Occurs to copy the genetic information from one cell to another Enzymes separate the two strands

from the double helix and then synthesize two new strands in order to get two complete copies of the double helix. Because each strand can be used to

make the other strand, the strands are said to be complementary. DNA replication results in two DNA molecules each with one new

strand and one original strand The role of enzymes DNA polymerase is an enzyme that joins individual nucleotides to produce a new

strand of DNA. DNA polymerase also proofreads each new DNA strand, ensuring that each molecule is a perfect copy of the original.

RNA RNA Ribonucleic acid

Principle molecule that carries out the instructions coded in DNA

RNA vs. DNA 1. RNA contains ribose instead of deoxyribose like DNA. 2.RNA contains uracil instead of thymine

3. RNA is a single strand instead of double-stranded. RNA is complementary to one DNA strand. The three main types of RNA are messenger RNA (mRNA), ribosomal

RNA (rRNA), and transfer RNA (tRNA). Transcription During transcription, segments of DNA serve as templates to produce complementary mRNA molecules. The base sequences of the transcribed RNA

complement the base sequences of the template DNA. . RNA Polymerase

RNA polymerase binds to DNA during transcription and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which to assemble nucleotides into a complementary strand of

mRNA. Genetic Code The sequence of amino acids that give a person his or her genetic

information. The specific amino acids in a polypeptide, and the order in which they are joined, determine the properties of different proteins.

The sequence of amino acids influences the shape of the protein, which in turn determines its function.

Each three-letter word in mRNA is known as a codon. A codon consists of three

consecutive bases that specify a single amino acid to be added to the polypeptide chain. Ribosomes use the sequence of codons in mRNA to assemble amino acids

into polypeptide chains. The decoding of an mRNA message into a protein is a process known as translation.

Translation begins when a ribosome attaches to mRNA

the ribosome reads each codon of mRNA, and directs tRNA to bring the specified amino acid to the ribosome.

the ribosome attaches each amino acid to the growing chain. What is the central dogma of

molecular biology? The central dogma of molecular biology is that information is transferred from DNA to RNA to protein.

One of the most interesting discoveries of molecular biology is the near-universal nature of the genetic code.

Despite their enormous diversity in form and function, living organisms display remarkable unity at lifes most basic level, the molecular biology of the gene. MUTATIONS

Types of Mutations 1. Gene Mutations produce

changes in a single gene 2. Chromosomal Mutations produce changes in whole chromosomes

Gene Mutations Mutations that involve changes in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence. They generally occur during replication.

Point Mutations Point mutations include substitutions, insertions, deletions, silent, missense and nonsense mutations. Substitutions

In a substitution, one base is changed to a different base. Substitutions usually affect no more than a single amino acid- missense, and sometimes they have no effect at all-silent.

Insertions and deletions are called frameshift mutations because they shift the reading frame of the genetic message. Frameshift mutations can change every amino acid that follows the point of the mutation and can alter a protein so much that it is unable to perform its normal functions.

Silent Mutations A mutation that does not change the resulting protein.

Does not change the amino acid sequence Missense Mutation

Change one amino acid in the resulting protein The meaning of one codon changes Nonsense Mutation A stop codon is inserted and shortens

the resulting protein Types of Chromosomal Mutations

Deletion Duplication Inversion Translocation Deletion

Deletion involves the loss of all or part of a chromosome. Duplication Duplication produces an extra copy of all or part

of a chromosome. Inversion Inversion reverses the direction of parts of a chromosome.

Translocation Translocation occurs when part of one chromosome breaks off and attaches to another. Effects of Mutations

How do mutations affect genes? The effects of mutations on genes vary widely. Some have little or no effect; and some produce beneficial variations. Some negatively disrupt gene

function. Ecology The Science of Ecology Ecology is the scientific study of interactions among and between organisms and their physical environment.

Levels of Organization Ecological studies may focus on levels of organization that include the following from smallest to largest: 1.

Organism-an individual living thing Ex. a catfish Levels of Organization 2. Populationa group of the same species living in the same area

Ex. all the spotted catfish in a lake Levels of Organization 3. Communitydifferent populations living together in a defined area

Ex. all the fish, amphibians, insects, etc. in/near a lake Levels of Organization 4. Ecosystemall organisms together with their physical environment Ex. all the fish, amphibians, insects,

etc. in/near a lake and other nonliving environmental features such as water, sunlight, and soil. Levels of Organization 5. Biomea group of ecosystems with similar climates and

organisms Ex. a large area of a continent Levels of Organization 6. Biosphere our entire planet

An organisms niche describes not only the environment where it lives, but how it interacts with living and nonliving factors in the environment. Biotic Factors

A biotic factor is any living part of the environment with which an organism might interact, including animals, plants, mushrooms and bacteria. Abiotic Factors An abiotic factor is any nonliving part of the environment, such as sunlight, heat, precipitation, humidity, wind or water currents, soil type, etc.

Primary Producers Primary producers are also called autotrophs because they use energy from the sun to change simple, non-living chemical nutrients (water & carbon dioxide) in the environment into living tissue during photosynthesis.

Energy From the Sun Photosynthesis captures light energy and converts carbon dioxide and water into oxygen and energyrich carbohydrates Plants- land Algae (phytoplankton)aquatic Life Without Light In the absence of light, the use of chemical

energy to produce carbohydrates is called chemosynthesis. Consumers Also called heterotrophs because they must feed on other organisms to obtain energy Types of Consumers

Consumers are classified by the ways in which they acquire energy and nutrients. a. Herbivores obtain energy by eating autotrophs - eat plant leaves, roots, seeds, or fruits. -cows, caterpillars, and deer. Types of Consumers

b. Carnivores -eat other animals - snakes, dogs, cats, and lions Types of Consumers c. Omnivores -eat both plants and animals -Humans, bears, and pigs Types of Consumers

d. Scavengers-consume carcasses of other animals. -Vultures Types of Consumers e. Decomposers- chemically break down organic matter to detritus- pieces of dead

and decaying remains -bacteria and fungi Types of Consumers f. Detritivores-, feed on detritus - earthworms Food Chains and Food

Webs Energy flows through an ecosystem in a one-way stream, from primary producers to various consumers. Food Chains A food chain is a series of steps in which organisms

transfer energy by eating and being eaten. The direction of the arrow represents the flow of energy from one organism to another. Food Webs In most ecosystems, feeding relationships

are much more complicated. A food web is a set of interconnected food chains by which energy and materials circulate within an ecosystem. Decomposers and Detritivores in Food Webs Without decomposers, nutrients would remain

locked in dead organisms. Trophic Levels and Ecological Pyramids Each step in a food chain or food web is called a trophic level. Primary producers always make up the first trophic level.

Various consumers occupy every other level. Trophic Levels and Ecological Pyramids Ecological pyramids show the relative amount of energy or matter contained within each trophic level in a given food chain or food web.

1. Pyramids of Energy amount of energy available at each trophic level only 10% of the energy that passes through any given trophic level is ultimately stored in the bodies of

organisms at the next level 2. Pyramids of Biomass total amount of living tissue within a given trophic level biomass the greatest biomass is at the base of the

pyramid 3.Pyramids of Numbers the relative number of individual organisms at each trophic level Cycles of Matter

Recycling in the Biosphere Biogeochemical cycles of matter pass the same atoms and molecules around again and again- matter is recycled

The Water Cycle 1. Evaporation and transpiration- evaporating from the leaves of plants 2. precipitation- rain, snow, sleet, or hail 3. runoff- water flowing along the surface 4. groundwater- water absorbed into the soil Nutrient Cycles

The chemical substances that an organism needs to sustain life are called nutrients. Where is Nitrogen found? 1.Nitrogen found in soil 2.Dissolved in the ocean and other water 3.Nitrogen gas (N2) -78 percent of Earths atmosphere; unusable for humans

The Nitrogen Cycle 4. nitrogen fixing bacteria- live in the soil ;can convert nitrogen gas into ammonia, nitrates, and nitrites that primary producers can then use -nitrogen fixation. The Nitrogen Cycle

5. denitrifying bacteria convert nitrogen solids into nitrogen gas, which is released into the atmosphere- denitrification The Nitrogen Cycle Humans add nitrogen to the biosphere through the manufacture and use of fertilizers-often carried into surface water

which can cause problems in aquatic ecosystems The Carbon Cycle 1. 2.

Plants take in carbon dioxide during photosynthesis and build carbohydrates which pass to consumers. Organisms release carbon in the form of carbon dioxide gas by respiration. The Carbon Cycle

3. When organisms die, decomposers release carbon back to the environment. 4. Geologic forces turn carbon into rocks or fossil fuels. The Carbon Cycle 5. Carbon dioxide is released into the

atmosphere by volcanic activity or by human activities, such as the burning of fossil fuels and the clearing and burning of forests. Nutrient Limitation primary productivitythe rate at which primary producers create organic material.

If an essential nutrient is in short supply, primary productivity will be limited. The nutrient whose supply limits productivity is called the limiting nutrient. Nutrient Limitation in Aquatic Ecosystems Sometimes an aquatic ecosystem receives a large input of a limiting nutrientfor example,

phosphorus runoff from heavily fertilized fields, causing an algal blooma dramatic increase in the amount of algae and other primary producers due to the increase in nutrients. If there are not enough consumers to eat the algae, an algal bloom can cover the waters surface and disrupt the functioning of an ecosystem.

Niches and Community Interactions Tolerance Organisms have an upper and lower limit of tolerance for every environmental factor which determines habitat. Beyond those limits, the organism is too stressed and cannot survive.

Competition Competition occurs when organisms attempt to use the same limited ecological resource in the same place at the same time. Competition In a forest, for example, plant roots compete for

resources such as water and nutrients in the soil. Animals compete for resources such as food, mates, and places to live and raise their young. between members of the same species intraspecific between members of different speciesinterspecific Predator-Prey

Relationships An interaction in which one animal (the predator) captures and feeds on another animal (the prey) is called predation. Predators can affect the size of prey populations in a community and determine the places prey can live and feed.

Herbivore-Plant Relationships An interaction in which one animal (the herbivore) feeds on producers (such as plants) is called herbivory. Symbioses

Any relationship in which two species live closely together is called symbiosis, which means living together. Mutualism Mutualism a relationship between two species in which both benefit

Parasitism Parasitism, relationships in which one organism lives inside or on another organism and harms it Tapeworms, fleas, ticks, lice, and leeches Commensalism

Commensalism- one organism benefits and the other is neither helped nor harmed. Succession Primary Succession When existing communities are completely destroyed by disturbances,

succession that begins in this area with no remnants of an older community is called primary succession. Ex>Volcanic explosions or retreating glaciers leaving only exposed bare rock Primary Succession

The first species to colonize barren areas are called pioneer species. Ex>lichens convert, or fix, atmospheric nitrogen into useful forms for other organisms, break down rock, and add organic material to form soil. Secondary Succession

secondary succession -existing communities not completely destroyed by disturbances Secondary succession proceeds faster than primary succession, in part because soil survives the disturbance. Biomes

Defining Biomes Ecologists classify Earths terrestrial ecosystems into at least ten different groups of regional climate communities called biomes. Biomes are described in terms of abiotic factors like climate and soil type, and biotic factors like plant and animal life.

Defining Biomes The map shows the locations of the major biomes. Defining Biomes Organisms within each biome can be characterized by adaptations that enable them to live and reproduce

successfully in the environment. Aquatic Ecosystems Water Depth Water depth strongly influences aquatic life because sunlight penetrates only a

relatively short distance through water. The sunlit region near the surface in which photosynthesis can occur is known as the photic zone. Below the photic zone is the dark aphotic zone, where photosynthesis cannot occur. Freshwater Ecosystems

Freshwater ecosystems include streams, lakes, and freshwater wetlands (bogs, swamps, and marshes). Freshwater Wetlands A wetland is an ecosystem in which water either covers the soil or is present at or near the surface for at least part of the year. Water may flow through freshwater

wetlands or stay in place. Wetlands are often nutrient-rich, highly productive, and serve as breeding grounds for many organisms. Estuaries An estuary is a special kind of wetland, formed where a river meets the sea.

Estuaries contain a mixture of fresh water and salt waterbrackish water How Populations Grow Birthrate and Death Rate A population can grow when its

birthrate is higher than its death rate. If the birthrate equals the death rate, the population may stay the same size. If the death rate is greater than the birthrate, the population is likely to shrink.

Immigration and Emigration A population may grow if individuals move into its range from elsewhere, a process called immigration.

A population may decrease in size if individuals move out of the populations range, a process called emigration. Exponential Growth If you provide a population with all the food and space it needs, protect it from predators and disease, and

remove its waste products, with unlimited resources, a population will grow exponentially. In exponential growth, the larger a population gets, the faster it grows. The size of each generation of offspring will be larger than the generation before it.

Logistic Growth What is logistic growth? Logistic growth occurs when a populations growth slows and then stops following a period of exponential growth Logistic Growth

Natural populations dont grow exponentially for long. Sooner or later, something stops exponential growth. What happens? Carrying Capacity Carrying capacity is the maximum number of individuals of a particular species that a

particular environment can support. Once a population reaches the carrying capacity of its environment, a variety of factors act to stabilize it at that size. Limits to Growth

Limiting Factors A limiting factor is a factor that controls the growth of a population. Density-Dependent Limiting Factors

What limiting factors depend on population density? Density-dependent limiting factors include competition, predation, herbivory, parasitism, disease, and stress from overcrowding. Competition

Competition is a density-dependent limiting factor. The more individuals living in an area, the sooner they use up the available resources. Predation and Herbivory The effects of predators on prey and the effects of herbivores on plants are two very important

density-dependent population controls. Herbivore Effects Herbivory can also contribute to changes in population numbers. From a plants perspective, herbivores are predators.

Parasitism and Disease Parasites and disease-causing organisms feed at the expense of their hosts, weakening them and often causing disease or death. Parasitism and disease are density-dependent effects, because the denser the host population, the more easily parasites can spread from one host to another.

Stress From Overcrowding Some species fight amongst themselves if overcrowded. Too much fighting can cause high levels of stress, which can weaken the bodys ability to resist disease. In some species, stress from overcrowding can cause females to neglect, kill, or even eat their own offspring.

. Density-Independent Limiting Factors What limiting factors do not typically depend on population density? Unusual weather such as hurricanes, droughts, or floods, and natural

disasters such as wildfires, can act as density-independent limiting factors. A severe drought can kill off great numbers of fish in a river.

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