Continuity of life-forms
B-5.2: Explain how genetic processes result in the
continuity of life-forms over time.
Continuity of life-forms
 Continuity of life-forms on
Earth is based on an
organism’s success in passing
genes to the next generation
 Organisms from years ago
resemble those alive today
 Because same genetic
processes have passed
along the genetic material
of life (DNA!!!)
Continuity of life-forms
 Most scientists attribute the continuity of life-forms over time
to the genetic processes that all organisms share.
 All life on Earth, share at least the same 2 structures
 Nucleic acids (RNA or DNA) carry code for protein synthesis
 Proteins (all life composed of same 20 amino acids)
 Transcription and translation (nucleic acids coding for
proteins) is same in all life on Earth
 Same sequence of nucleotides code for same specific amino acids
 Example: AUG always codes for methionine no matter the
organism
Passing Genetic information
 All organisms have reliable means of passing
genetic information to offspring through
reproduction
 Reproductive processes result in offspring receiving
essentially the same genetic information as
parents, can be some genetic variability
 Two types of reproductive processes
 Sexual reproduction
 Asexual reproduction
Sexual Reproduction
 Uses meiosis to create gametes
 Fertilization results in embryo receiving alleles from each
parent for each trait
 Offspring will express a combination of traits allowing for
variation
Sexual Reproduction and genetic
variability
 Genetic variability through sexual reproduction, due to:
 Gene shuffling, Crossing over, Recombination of DNA,
Mutations
 When gametes are produced, alleles are arranged in new ways
in the offspring
Sexual Reproduction and genetic
variability
 Genetic changes result in transcription and translation of
new/different proteins that will result different phenotypes of
an individual organism
 Reproduction results in allele combinations producing traits
that improve an organism’s chance of survival ensure the
continuity of that life form over time.
Sexual Reproduction and genetic
variability
Asexual Reproduction
 Involves only one parent
 Produces offspring that are for the most part
genetically identical to parent
Methods of asexual reproduction
 Asexual reproduction accomplished
by cell division
 Binary fission (single-celled
organisms)
 Mitosis (multi-celled organisms)
 Examples of asexual reproduction:
budding, fragmentation, and
vegetative propagation
Asexual Reproduction and Genetic
Variability
 Genetic variability in asexual
reproduction can only occur in
mutations in DNA passed from
parent to offspring
 A way that organisms achieve
variations as populations
continue over time
Pros and Cons of asexual reproduction
 Pro: reproduction rate is much higher
than sexual reproduction
 Produces many offspring that are
suited to continuing life in the
present environment
 Con: genetically identical offspring
respond to the environment in the
same way
 If a population lacks traits that
enable them to survive and
reproduce, the entire population
could die off
Genetics of Evolution
 Genetic view of evolution includes
the transfer of the genetic material
through sexual and asexual
reproduction.
 The continuity of a species is
contingent upon these genetic
processes
 If an organism can reproduce both
sexually and asexually, they have an
adaptive advantage for survival.