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Heredity and Evolution Review. Life Science 7 Ms. McCarthy. Heredity! . Heredity is the passing of traits from parent to offspring. Traits (phenotypes) are the result one or more gene, that contain directions to make the trait (ex: eye color, height, ear lobe shape.)

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heredity and evolution review

Heredity and Evolution Review

Life Science 7

Ms. McCarthy

  • Heredity is the passing of traits from parent to offspring.
  • Traits (phenotypes) are the result one or more gene, that contain directions to make the trait (ex: eye color, height, ear lobe shape.)
  • How an organism ends up with a trait, is by the alleles they have for that trait.
  • Alleles are the different ways a trait can be expressed.
alleles and genotypes
Alleles and Genotypes
  • So a trait has a phenotype and genotype.
  • Phenotype is what you can observe.
  • Genotype is a 2 letter code that says what alleles an organism has.
  • An organism can be 1/3 things based on the alleles they inherit (1 from each parent, represented by a letter that is capital for dominant, or lower case for recessive.)
    • Ex: AA, Aa, aa
genotype vs phenotype
Genotype vs. Phenotype
  • Ok, so let’s say we are talking about hair style.
punnett squares
Punnett Squares
  • Are a tool for predicting the probability the offspring of 2 organisms will have a certain phentoype. Any letters can be used to represent alleles.
analyzing punnett squares
Analyzing Punnett Squares
  • Here is a cross of 2 parents.
  • Both are Heterozygous: Aa
  • Chances are, they will have
  • 50% heterozygous offspring
  • 25% homozygous dom.
  • 25% homozygous recessive
  • This explains why sometimes offspring do not look much like the parents!
incomplete dominance
Incomplete Dominance
  • Sometimes an organism’s phenotype shows a cross between the dominant and recessive trait.
    • Examples: wavy hair (inbetween curly and straight)
    • Light blue flower (inbetween blue and white)

This is called incomplete dominance.

polygenic inheritance and mutations
Polygenic Inheritance and Mutations
  • Most traits are not as simple as a punnett square makes it look- multiple genes contribute to what the phenotype looks like– this is called polygenic inheritance.
  • Mutations are disruptions to DNA and are caused by many factors. They can be helpful, harmful or have no effect.
  • Father of Genetics
  • Experimented with Pea Plants with traits such as flower color, pea color, pea texture.
  • He made 3 important contributions we call laws:
    • Law of segregation
    • Law of dominance
    • Law of independent assortment
the laws know em
The laws! (Know em’)
  • Dominance: In a cross of parents that are pure (homozygous) for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are heterozygous for a trait will have only the dominant trait in the phenotype.
    • 2 homo dominant parents= offspring all homo dominant
    • 1 homo dominant with 1 hetero= offspring 2 homo dom, 2 hetero
    • 1 homo dominant with 1 homo recessive= 4 hetero
    • 2 hetero= 1 homo dom, 1 homo rec, 2 hetero
    • 2 homo recessives= 4 homo recessives
  • Segregation: During the formation of gametes (eggs or sperm from meiosis), the two alleles responsible for a trait, separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.
    • Sperm contributes A, egg contributes a, zygote will be Aa genotype
  • Ind. Assortment: Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
    • A parent can pass a dominant allele for one trait and a recessive for another that does not show in their phenotype.
sex linked traits
Sex-linked traits
  • Some traits are linked to the X or Y chromosome.
  • These are called sex linked traits.
  • It is not possible for asexually reproducing organisms to have sex-linked traits or disorders…only those that do meiosis- sexual reproduction.
advances in genetics
Advances in Genetics
  • Genetic Engineering
  • Making recombinant DNA
  • Gene Therapy
  • GMO plants/genetically-engineered plants
  • How species (groups of organisms that share similar characteristics) change over time due to the inherited characteristics from their parent organisms.
  • Darwin’s theories made the main body of evidence for evolution.
  • His studies occurred in the Galapagos islands.
darwin vs lamarck
Darwin vs. Lamarck
  • Lamarck thought that if an organism changed themselves during their lives, the offspring would have those traits.
    • This would mean a bodybuilder’s kids would inherit HUGE muscles. This is not accurate.

Darwin’s theory of the origin of species contains several important vocab words that explain how species change over time.

darwin s observations
Darwin’s Observations
  • Organisms that are best-suited for an environment reproduce; those that are not, die off. This makes those with the best traits more common, and they continue to compete with one another. This is the idea of natural selection.
  • All organisms tend to have more babies than will live, because they must compete with each other for resources, and the best-suited win and then then continue to reproduce. This is called overproduction.
observations continued
Observations continued.
  • Variation is when a trait is slightly different from other traits in a species. Sometimes these changes are small mutations, sometimes they are large. Variation is good because it creates changes that may benefit the species.
  • When traits are passed on for a long time, the best traits tend to be most common which is how organisms are best adapted for their environments. Being well-suited based on your traits, is what adaptation is.
  • The environment demands the traits!
  • Sometimes new species are formed when a group of a species is isolated from the rest. This could cause one group to remain the same, while the other over time becomes a new species.
speed of evolution
Speed of Evolution
  • Evolution can happen fast, although it is usually something that takes millions of years.
  • FAST: Punctuated Equilibrium can occur from rapid mutations and reproduction, or when a large portion of a species does not survive something due to a specific trait that will no longer exist.
    • Drug-resistant bacteria is one example.
speed continued
Speed continued:
  • SLOW: Gradualism is when one species changes to another very slowly. This is how most species today got to be their current forms.
evidence of evolution
Evidence of Evolution
    • We can see that similar things evolved at the same time because of how fossils are found in the same rock layers.
      • This is relative dating.
    • We can also see how older layers have less evolved organisms, and with each new layer has more evolved organisms from the last layer.
      • This is called the fossil-record.
    • Radiometric dating is using scientific technology to determine how old a fossil is. Elements contained in the fossils have measurable radioactivity that is slowly breaking down.
more evidence
More Evidence
    • Even complex organisms share traits with things that are much less evolved. For example, human embryos have tails, gills, webbed hands and feet.
more evidence1
More Evidence…
    • Why would whales have leg ones? Because they evolved from land mammals that used legs! The structures are vestigial, and have not gone away yet, but might eventually.
more evidence2
More Evidence….
    • Have you ever noticed how a hand, wing, flipper and paw all kind of look the same? These are called homologous structures because they serve similar functions but have bone structures that link them all together.
    • Think about what makes all things within the same kingdoms and sub-kingdoms similar.
more evidence3
More Evidence:
  • DNA:
    • You have more DNA in common with a fly or a type of bacteria than you might think.
    • This shows shared ancestry.
  • Keys to human evolution!
  • Think of all the things that link humans to monkeys.
  • What about:
    • Prosimians
    • Anthropoids
    • Hominids
    • Homo Habilis
    • Australopithecus
    • Homo Neanderthalis
    • Cro-Magnon