MCAS Review Biology

HS-LS1-1.  Construct a model of transcription and translation to explain the roles of DNA and RNA that code for proteins that regulate and carry out essential functions of life. 

Structure of DNA:

• Made of nucleotide  building blocks

• Double Helix: two strands form a spiral or twisted ladder

• Sides are made of alternating sugar (named deoxyribose)  and phosphate

• Rungs are made of nitrogen base pairs

• Adenine (A) pairs with Thymine (T)

• Cytosine (C)  pairs with Guanine (G)

• Example: If one side of a strand is ATCG, 

  the other side is TAGC

Function of DNA in genetic inheritance: 

• Genes are codes for an organism’s traits

• Genes are sequences of nitrogen bases on a DNA strand 

• Chromosomes are made of DNA

• Chromosomes (DNA containing  genes) are passed in eggs and sperm from parents to offspring during reproduction

GENE EXPRESSION: Protein Synthesis

• DNA → mRNA → Protein

• Two stages: Transcription and Translation

• Involves RNA

  • single stranded chain of nucleotides

  • has Ribose sugar instead of deoxyribose sugar

  • uses Uracil instead of Thymine

  • Three types: 

mRNA-  messenger

rRNA – ribosomal

tRNA – transfer 

Transcription- making an RNA copy of DNA (DNA → mRNA)

• Occurs in the nucleus

• DNA unzips along a gene

• Complementary RNA nucleotides fall into place along the gene

(C-G;  G-C,  T-A BUT DNA Adenine pairs with RNA Uracil)

* mRNA detaches and leaves the nucleus; DNA zips up

Translation – building a protein out of a sequence of amino acids directed by the mRNA                  ( mRNA → protein)

• mRNA attaches to a ribosome in the cytoplasm

• every three mRNA nitrogen bases is called a codon

• tRNA  are found floating in the cytoplasm

• tRNA carry specific amino acids to the ribosome

• tRNA anticodons attach to mRNA codons in order 

• tRNA  leave their amino acids and detach from mRNA

• amino acids join together to form a protein (polypeptide)

• the protein will perform a function or make a structure for the organism

The Genetic Code: use this codon chart to translate mRNA codons into amino acids

Example: mRNA:     AUG -     GUC -   CAA -  UGA = 

     Amino acids: Met (start) – valine – glutamine – stop

Circle version codon chart:

Mutations: a change in the sequence of nucleotides in DNA or RNA

Original Sequence mRNA:     AUG -     GUC -   CAA -  UGA = 

     Amino acids: Met (start) – valine – glutamine – stop

Possible Mutation Effects :

1)  Example:  Change the mRNA above to AUG- CUC –CAA –UGA

Amino acids change to :  met(start) – leucine –glutamine –stop

Consequence: Phenotypic change : this new protein may be harmful (or beneficial) to the organism 

2) Example: Change the mRNA to AUG- GUG –CAA –UGA

Amino acids remain:   met – valine – glutamine –stop

Consequence: NO phenotypic change  : this is a harmless mutation; the protein is the same

3) Mutations in gametes (eggs and sperm) will be passed on to offspring; mutations in body cells will NOT be passed on to offspring but MAY cause disease in the organism

More mutation examples...

HS-LS1-2. Develop and use a model to illustrate the key functions of animal body systems, including (a) food digestion, nutrient uptake, and transport through the body, (b) exchange of oxygen and carbon dioxide, (c) removal of wastes, and (d) regulation of body processes. 

Each villi contains a

capillary to absorb the 

food digested (broken into 

monomers) in the small

intestine.

This blood, rich with 

absorbed nutrients will

next go to the liver.

Villi also greatly increase the

surface area through which

you can digest and absorb 

your food

*Urea is a toxic byproduct of amino acids being broken down in the body. This “nitrogenous waste” is made in the liver and excreted with the urine (and also in the sweat).

Liver: Receives and processes blood from the digestive tract

Monitoring and regulating the body and its responses is carried out by both the nervous system and the endocrine system (hormones):

HS-LS1-3. Provide evidence that homeostasis maintains internal body conditions through both body-wide feedback mechanisms and small-scale cellular processes. 

1. Body Wide Homeostasis

Homeostasis = Maintaining relatively stable internal conditions

Negative feedback = When a change in a variable triggers a response which reverses the initial change. Negative feedback is used by the body to maintain homeostasis.

Example: Insulin and glucose regulation by negative feedback. (Graph shows when blood glucose goes up, the hormone insulin acts to reverse the change).

If negative feedback loops are not working properly, the body can lose homeostasis and become unbalanced. An example of this is the disease diabetes.

In diabetes, there is a problem with insulin and it 

does not open glucose channels like it should.  

Glucose builds up in the blood instead, leading 

to the symptoms of the disease.

Positive feedback does NOT play a role in maintaining homeostasis.  It is the opposite of negative feedback.  A change in a variable in the body causes more change in the variable to keep amplifying the response.

BLOOD CLOTTING with platelets attracting more and more (and more!) platelets to the area is an example of positive feedback.

2. Small Scale (Cell-level) Homeostasis

• Lysosomes are an organelle that play a role in maintaining internal conditions inside of cells.  They have digestive enzymes and can break down molecules that the cell does not need, wastes, and old cell parts into monomers.  They can destroy bacteria and viruses and can even play a role in destroying the entire cell (apoptosis) if needed.

• Plasma membranes play a role in maintaining homeostasis (stable internal conditions for the cell).  They are selectively permeable, allowing some substances to enter or leave the cell while others cannot.  The structure of the membrane is important in understanding this selective permeability.

Membranes are made of a bilayer of phospholipids 

• Proteins also play an important role in the selective permeability of plasma membranes.

  • While some nonpolar and small molecules can diffuse directly through the plasma membrane, many others cannot just pass by simple diffusion (movement from high to low concentration) or osmosis.

• Proteins in the membrane that can act as carriers or channels allow other needed molecules to enter/exit the cell by facilitated diffusion.

• A last option for moving molecules into/out of cells is active transport. This requires the cell to use ATP (energy) to move the molecule against its concentration gradient (from low to high concentration).

Passive transport does not use energy (ATP), there are 3 types 

1. Diffusion = Molecules move from where they are more concentrated to where they are less concentrated.

2. Facilitated diffusion: Molecules move from where they are more concentrated to where they are less concentrated using a protein channel or carrier  to get into the cell.

3. Osmosis: Water diffuses across a cell membrane from where it is more concentrated to where it is less concentrated through aquaporin channels.

Active transport = Requires energy (ATP) to force a molecule to move from where it is less concentrated to where it is more concentrated.  Active transport in a cell includes pumps as well as endocytosis (engulfing molecules) and exocytosis (releasing molecules in vesicles).

Cells in various solutions will respond to achieve homeostasis by gaining or losing water:

HS-LS1-4. Construct an explanation using evidence for why the cell cycle is necessary for the growth, maintenance, and repair of multicellular organisms. Model the major events of the cell cycle, including (a) cell growth and DNA replication, (b) separation of chromosomes (mitosis), and (c) separation of cell contents. 

Cell Cycle

S Phase of Interphase = DNA replication (making an exact copy of a DNA molecule)

• DNA unzips

• Complementary bases fall into place on each side of the open strand following base pairing rules (A pairs with T;C pairs with G)

• Two identical strands are created, each with one old strand and one new strand

• Replication insures each new cell receives an exact copy of its genetic code

In mitosis the replicated chromosomes are separated into two identical daughter cells (each get their own copy of the DNA)

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HS-LS1-5. Use a model to illustrate how photosynthesis uses light energy to transform water and carbon dioxide into oxygen and chemical energy stored in the bonds of sugars and other carbohydrates.   

Additional Guidelines

HS-LS1-6. Construct an explanation based on evidence that organic molecules are primarily composed of six elements, where carbon, hydrogen, and oxygen atoms may combine with nitrogen, sulfur, and phosphorus to form monomers that can further combine to form large carbon-based macromolecules. 

More About Important Proteins…

1. Enzymes: Speed up chemical reactions by lowering activation energy of the chemical reaction

2. Hormones & receptors: Some hormones are proteins (and some are lipids).  Every hormone has a unique receptor protein that it binds to on a target cell.  The binding triggers a response in the target cell.

3. Structural proteins: Proteins in our muscles allow them to contract (actin and myosin protein), collagen and keratin  proteins give structure to our skin, nails, and hair 

HS-LS1-7. Use a model to illustrate that aerobic cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and new bonds form resulting in new compounds and a net transfer of energy.  

Aerobic cellular respiration = a series of chemical reactions that happen in the mitochondria and produce the energy (ATP) that powers all cellular processes

HS-LS2-1. Analyze data sets to support explanations that biotic and abiotic factors affect ecosystem carrying capacity.  

Biotic = Living parts of an ecosystem 

(examples   = trees, insects, bacteria, mold)

Abiotic = Non-living parts of an ecosystem (examples = rocks, soil, weather, water)

Carrying capacity = refers to the maximum number of individuals of a species that the environment can carry and sustain

Ecosystem = All of the living and nonliving factors in an area

Community = All of the living things in a certain area

Population = All of the members of one species in a certain area

Immigration = New organisms enter a population (think “Imm sounds like In”)

Emigration =  Organisms leave a population (think “e” is for “exit”)

Predation = One organism (predator) eats another organism (prey)

Competition = Two different organisms try to use the same resources (also known as limiting factors)

Symbiosis = A close and long-term biological interaction between two different species.  The three kinds are mutualism, commensalism, and parasitism as shown here:

Carrying capacity = refers to the maximum number of individuals of a species that the environment can carry and sustain

Examples of biotic factors that could affect ecosystem carrying capacity:

• Feeding relationships (example - new predator introduced could lower carrying capacity)

• Symbiosis (example - parasitism might lower carrying capacity)

• Competition 

• Disease

Examples of abiotic factors that could affect ecosystem carrying capacity:

• Climate & weather conditions (good climate years could increase carrying capacity)

• Natural disasters

• Availability of resources (soil, minerals, water, etc)

HS-LS2-2. Use mathematical representations to support explanations that biotic and abiotic factors affect biodiversity, including genetic diversity within a population and species diversity within an ecosystem.  

Biotic = Living parts of an ecosystem (examples = trees, insects, bacteria, mold)

Abiotic = Non-living parts of an ecosystem (examples = rocks, soil, weather, water)

Biodiversity = the variety of life found in a  place (or on the Earth).  There are three types: genetic diversity, species diversity, and ecosystem diversity.

Genetic diversity = The variety of alleles for genes and genotypes present.  A group with high genetic diversity has a lot of variation in the gene pool and low genetic diversity has little variation with organisms having very similar alleles for their traits.

Species Diversity  = The number of different species in an area and the abundance of each species.

Ecosystem = All of the living and nonliving factors in an area

Examples of biotic factors that could affect biodiversity:

• Feeding relationships (example - new predator introduced could lower biodiversity)

• Competition 

• Disease

• Symbiosis (example - parasitism might lower biodiversity)

Examples of abiotic factors that could affect biodiversity:

• Climate & weather conditions (good climate could increase the number of species able to live in the area)

• Natural disasters

• Availability of resources (soil, minerals, water, etc)

HS-LS2-4. Use a mathematical model to describe the transfer of energy from one trophic level to another. Explain how the inefficiency of energy transfer between trophic levels affects the relative number of organisms that can be supported at each trophic level and necessitates a constant input of energy from sunlight or inorganic compounds from the environment. 

Trophic level = (“feeding level”) Each level in a food chain or food web.  Primary consumer, secondary consumer, etc.

Inorganic Compounds= A molecule without carbon; a molecule not found in living things

Producer = Organisms that can make their own food (plants and some protists and some  bacteria)

Primary Consumer (Herbivore) = Organisms that eat producers (herbivores)

Secondary Consumer (Carnivore) =Organisms that eat primary consumers (carnivores)

Tertiary Consumer = Organisms that eat secondary consumers

Apex Predator = Predator  that is at the top of the food chain

Decomposer = Organisms that break down dead or dying organisms (fungi and some bacteria)

Autotroph (“self feeding”) - Organisms that produce their own food (aka producers)

Heterotroph (“other feeding”) - Organisms that consume their food

HS-LS2-5. Use a model that illustrates the roles of photosynthesis, cellular respiration, decomposition, and combustion to explain the cycling of carbon in its various forms among the biosphere, atmosphere, hydrosphere, and geosphere.  

Decomposition: Dead organisms release their carbon into the soils, these can get compacted into hydrocarbons

Combustion: Burning fossil fuels or burning trees and vegetation releases carbon dioxide back into the atmosphere

Biosphere: Regions of the earth occupied by living things

Atmosphere: The gasses surrounding the earth

Hydrosphere: The waters on the surface of Earth

Geosphere: Solid parts of the earth

Hydrocarbons: Chains of carbon and hydrogen found in fossil fuels

Biomass: The total mass of organisms in an area.  In the carbon cycle, carbon exists in the molecules of living things, so biomass is a form that carbon is stored in.

Carbonic Acid: Carbon dioxide dissolved in water can react to form carbonic acid; this is leading to ocean acidification.

Adds carbon dioxide to atmosphere =

Cellular respiration, combustion (fossil fuels, lumber/plants), Volcanos

Removes carbon dioxide from atmosphere = Photosynthesis

Adds carbon to biosphere = Photosynthesis, consumption

Removes carbon from biosphere = death & decomposition

Adds carbon to geosphere & hydrosphere:  death & decomposition 

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Data shows that increasing carbon dioxide in the air corresponds to rising global temperatures:

Carbon dioxide (and methane from agriculture) are “greenhouse gasses” that are trapping more sunlight energy and causing the climate to warm

HS-LS2-6. Analyze data to show ecosystems tend to maintain relatively consistent numbers and types of organisms even when small changes in conditions occur but that extreme fluctuations in conditions may result in a new ecosystem. Construct an argument supported by evidence that ecosystems with greater biodiversity tend to have greater resistance to change and resilience. 

• Ecosystems will stay relatively stable in number and type of organisms unless disturbed

• Small disturbances will not cause the ecosystem to change significantly

• Examples of small/medium disturbances could be seasonal floods or seasonal hunting

• Extreme disturbances can have a drastic impact and can even cause a new ecosystem

• Extreme disturbance include: 

  • Volcanic eruption

  • Fire

  • Climate change

  • Ocean acidification

  • Sea level rise

  • Loss or decline of a keystone species:

HS-LS2-7. Analyze direct and indirect effects of human activities on biodiversity and ecosystem health, specifically habitat fragmentation, introduction of non-native or invasive species, overharvesting, pollution, and climate change. Evaluate and refine a solution for reducing the impacts of human activities on biodiversity and ecosystem health.

Habitat fragmentation: Parts of a habitat are destroyed and leaves behind smaller, unconnected areas for wildlife:

Invasive (non-native) species = an introduced species (non-native) that causes great ecological and/or economic harm.  Invasive species may not have predators in the new location or they may kill, harm, or out-compete the native species for resources.  Some invasive species are able to reproduce quickly in their new environment and become a problem for humans and other wildlife.

Overharvesting: The harvesting of plants or animals at an unsustainable level, causing harm to the ecosystem.  Examples: overfishing, overhunting.

Pollution: Releasing harmful substances into the air, water, or land that can damage native ecosystems.

Examples of Solutions:

• captive breeding programs

• habitat restoration

• pollution mitigation (strategies to remove pollutants from habitats and stop releasing more pollutants)

• energy conservation

• ecotourism (tourism that aims to conserve natural resources and educate people about them)

HS-LS3-1. Develop and use a model to show how DNA in the form of chromosomes is passed from parents to offspring through the processes of meiosis and fertilization in sexual reproduction.  

Meiosis = type of cell division that produces gametes (sperm and egg cells).  The gametes are haploid, meaning they have only one set of chromosomes instead of chromosomes in pairs.  So, sperm/egg have half the number of chromosomes as all other body cells.  

Fertilization = sperm and egg cell fuse to form the first cell of the new organism, which is called the zygote.  The zygote will have 46 chromosomes because it is diploid after receiving half of its chromosomes from the mother and half from the father.

Meiosis produces the haploid gametes. Fertilization produces the diploid zygote. Then, mitosis cell divisions of the zygote cause the embryo to grow and develop.

HS-LS3-2. Make and defend a claim based on evidence that genetic variations (alleles) may result from (a) new genetic combinations via the processes of crossing over and random segregation of chromosomes during meiosis, (b) mutations that occur during replication, and/or (c) mutations caused by environmental factors. Recognize that mutations that occur in gametes can be passed to offspring. 

Causes of genetic variation in the alleles of offspring:

1. Crossing over = DNA segments are exchanged between the non-homologous (maternal and paternal) chromosomes during meiosis as the egg or sperm cells are made.

2. Random segregation (aka independent assortment) of chromosomes during formation of egg or sperm cells: 

3. Mutations that happened during DNA replication in a parent and were present in the sperm/egg cell (if mutation is in another body cell but not sperm/egg it does not get passed to offspring).

4. Mutations that were caused by environmental factors in a parent and were present in the sperm/egg cell (if mutation is in another body cell but not sperm/egg it does not get passed to offspring).

HS-LS3-3. Apply concepts of probability to represent possible genotype and phenotype combinations in offspring caused by different types of Mendelian inheritance patterns.

Genotype:  The alleles an organism has for a trait (example = Rr)

Phenotype: The physical characteristics of an organism (example = round face)

Homozygous: Having two of the same alleles for a trait (example RR or rr)

Heterozygous: Having two different alleles for a trait (example Rr)

Example problem - simple autosomal dominant/recessive. If A = pink and a = blue and both parents are heterozygous. Show the Punnett:

Video clip: Punnett Square Basics

¾ possible offspring are pink and ¼ possible offspring are blue.

*individuals have two alleles for each gene

when gametes form by meiosis, the two alleles separate 

each resulting gamete ends up with only one allele of each gene

Inheritance Patterns

Incomplete dominance

Video clip 1 Incomplete & Codominant Punnetts Video clip 2

Polygenic:

Multiple alleles and Codominance

Video clip - blood type genotypes explained

Video clip solving blood type punnetts

Example: How to set up amd solve a dihybrid cross

A pea plant that is heterozygous for round, yellow seeds is self fertilized, what are the phenotypic ratios of the resulting offspring?

Step 1: Determine the parental genotypes from the text above, the word "heteroyzous" is the most important clue, and you would also need to understand that self fertilized means you just cross it with itself.

RrYy x RrYy

Step 2: Determine the gametes. This might feel a little like the FOIL method you learned in math class. Combine the R's and Ys of each parent to represent sperm and egg. Do this for both parents

Video clip - how to solve dihybrids

Gametes after "FOIL"

RY, Ry, rY, ry (parent 1) and RY, Ry, rY, ry (parent 2)

Step 3: Set up a large 4x4 Punnet square, place one gamete set from the parent on the top, and the other on the side

Step 4: Write the genotypes of the offspring in each box and determine how many of each phenotype you have. In this case, you will have 9 round, yellow; 3 round, green; 3 wrinkled, yellow; and 1 wrinkled green

Sex-linked Punnett Square:

Sex linked video clip

Pedigree for a sex-linked recessive trait: look for MANY MORE MALES (squares) with the trait.

Inheritance Patterns & Pedigrees

Autosomal Inheritance: gene/allele is located on an autosome (non-sex chromosome)

• Can be dominant or recessive

  • Dominant: DD & Dd affected

  • Recessive: dd affected

Sex-linked: gene/allele is located on a sex chromosome (X or Y)

• we only did recessive x linked

• Example X^hX^h = female affected

•  X^hY

Autosomal recessive pedigree: 

• look for 2 parents without trait and a kid who does have the trait

•  if there are 2 parents both with trait, all kids have to have it

•    Example:

Video clip about how to analyze pedigrees

Autosomal dominant pedigree: 

• look for everyone with trait has at least one parent with trait

• look for 2 parents that have it with a kid who does not have it (so parents must be Dd and kid dd)

•    Example:

HS-LS3-4(MA). Use scientific information to illustrate that genetic traits of individuals, and the presence of specific alleles in a population, are due to interactions of genetic factors with environmental factors. 

Examples of genetic factors

• Having multiple alleles for one gene

• Having multiple genes influencing a more complex trait

How can you tell if a trait is inherited with multiple alleles or multiple genes?  Look for a trait like skin color or eye color with many different phenotypes (not just 2).

Examples of environmental factors

• likelihood of developing inherited diseases (e.g., heart disease, cancer) in relation to exposure to environmental toxins and lifestyle

• the maintenance of the allele for sickle-cell anemia in high frequency in malaria-affected regions because it confers partial resistance to malaria.

• sickle cell gene is an example of a gene that could be helpful in one situation (fighting off malaria infections) but harmful in another (places without malaria, not having sickle cell genes is better)

HS-LS4-1. Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence, including molecular, anatomical, and developmental similarities inherited from a common ancestor (homologies), seen through fossils and laboratory and field observations.  

Evolution = a change in a species over time

Natural selection = the cause of evolution; the idea that living things vary and some varieties survive and reproduce (and pass on their genes) better than others

Common Ancestry = This involves the evolution of new species from an ancestral population.  More closely related organisms have a more recent common ancestor.

Cladograms:  Can be used to organize information about common ancestry of species

Endosymbiosis also supports the theory of evolution.  Multiple lines of evidence support the idea that mitochondria and chloroplast organelles in eukaryotic cells were once free floating bacteria that were engulfed and became a symbiotic organism (endosymbiosis), providing an energy source for the more complex cells.

HS-LS4-2. Construct an explanation based on evidence that Darwin’s theory of evolution by natural selection occurs in a population when the following conditions are met: (a) more offspring are produced than can be supported by the environment, (b) there is heritable variation among individuals, and (c) some of these variations lead to differential fitness among individuals as some individuals are better able to compete for limited resources than others. 

                       Natural selection

Biological Fitness = the ability to survive to reproductive age, find a mate, and produce offspring

Natural Selection

*selection pressure = a reason for organisms with certain traits to have either an advantage or a disadvantage for survival

Environmental selection pressures can allow some species to have similar traits even though they are NOT closely related.  This is convergent evolution. Example = animals in this diagram are not related closely, but they have all been naturally selected for a streamlined shape for swimming.

Environmental selection pressures can also  allow some species who ARE closely related to have different traits from each other as they adapt to different habitats. This is divergent evolution. 

HS-LS4-4. Research and communicate information about key features of viruses and bacteria to explain their ability to adapt and reproduce in a wide variety of environments.

Key Feature 1: relatively simple structure

Bacteria (prokaryote cells) Virus

no nuclei not a cell

no membrane bound organelles few structures

  (so no mitochondria, chloroplasts, golgi *nucleic acid wrapped in protein coat

   body, endoplasmic reticulum, etc)

bacteria & virus are simple when compared to eukaryotic cells (plants, animals, fungus, and protists):

Key Feature 2: relatively simple reproduction

Bacteria reproduce by binary fission

Viruses replicates by:

• Attaching to a host cell’s receptors

• Using the host cell to transcribe and translate copies of the virus nucleic acid (either DNA or RNA) and viral proteins

• Note: viruses can not reproduce by themselves, a host organism is required

   HOST

CELL

Key Feature 3: Quick reproduction because of simpler structures and reproduction 

   simpler methods

Eukaryotic species like humans reproducing with meiosis and sexual reproduction can take about 30 years to produce just one offspring.

Some species of bacteria can split by binary fission every 20 minutes.

Some viruses can attack a host cell and force it to start making new viruses within hours of infection.  Millions to billions of new viruses can be made each day.

When conditions are right, bacteria and viruses can reproduce fast and exponentially:

Key Feature 4: Quick reproduction results in many mutations and many generations of organisms in short time periods

Conclusion: many generations with high genetic diversity (because of mutations) means that natural selection and evolution of bacteria and viruses can happen quickly. They are good at adapting to and responding to new selection pressures.

An important example of this is the natural selection and evolution of antibiotic resistant bacteria:

HS-LS4-5. Evaluate models that demonstrate how changes in an environment may result in the evolution of a population of a given species, the emergence of new species over generations, or the extinction of other species due to the processes of genetic drift, gene flow, mutation, and natural selection. 

Environmental factors/selection pressures that can cause survival advantages/disadvantages →  causes changes in allele frequencies:

•  Availability of resources

• Predators

• Competition

• Climate Change

• Disease

• Science Skill: How can you analyze graphs/data to describe how selection pressures can drive reproductive advantages/disadvantages and survival advantages/disadvantages? 

Causes of changes in allele frequencies over time (so that a species can adapt and survive or new species can emerge over time):

1. Natural Selection

2. Mutations (beneficial or harmful)

3. Gene Flow

a. Immigration

b. Emigration

4. Genetic Drift random survival of some

a. Founder Effect b. Bottleneck Effect

Species = A group of organisms that naturally mates and produces fertile offspring

. 

Reproductive Isolation: the inability of a species to breed successfully with related species due to geographical, behavioral, physiological, or genetic barriers or differences.