Essay Exam Review_2015-05

1. Describe Mendel’s laws of inheritance. (10.2)

The Inheritance of Traits

Mendel’s law of segregation• The law of segregation states that the two alleles for each

trait separate during meiosis.

• During fertilization, two alleles for that trait unite.

• Heterozygous organisms are called hybrids.

The Inheritance of Traits

Law of independent assortment• The law of independent assortment states that random

distribution of alleles occurs during gamete formation.

• Genes on separate chromosomes sort independently during meiosis.

• Each allele combination is equally likely to occur.

Complex Inheritance PatternsIn incomplete dominance, the heterozygous phenotype is intermediated (inbetween) between two homozygous phenotypes.

2. Distinguish between incomplete and codominance. (11.2)

Complex Inheritance PatternsIn codominance, both alleles are expressed in heterozygotes.

3. Describe the structure of DNA. You may also include a sketch of the DNA molecule to help, however there must be written description of the molecule. (12.1)

DNA Structure

Nucleotides• Nucleotides are the subunits of nucleic acids, and consist of

• 5-carbon sugar

• Phosphate group

• Nitrogenous base

DNA Structure

DNA structure• DNA often is compared to a twisted ladder.

• Rails of the ladder are represented by the alternating deoxyribose and phosphate.

• The pairs of bases (cytosine-guanine or thymine-adenine) form the steps.

• Purine base always binds to a pyrimidine base

DNA Structure

Orientation• DNA molecules have specific orientations of the two strands

• One of the strands is said to be oriented 5’ to 3’.

• The other strand runs in the opposite direction and is oriented 3’ to 5’.

4. Describe what is meant by semiconservative replication. (12.2)

Semiconservative Replication• During semiconservative replication, parental strands of DNA

separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA.

• Process occurs in three main steps: unwinding, pairing, and joining.

Semiconservative Replication

Unwinding• DNA helicase, an enzyme, unwinds the helix, breaking the

hydrogen bonds between bases

• Single-stranded binding proteins keep the DNA strands separate during replication.

• RNA primase adds short segments of RNA primer, on each DNA strand.

Semiconservative Replication

Base pairing• The enzyme DNA polymerase adds appropriate nucleotides to the

new DNA strand from the 3’ end.

• The leading strand is built continuously, the lagging strand is built discontinuously in small segments called Okazaki fragments.

Semiconservative Replication

Joining• DNA polymerase removes the RNA primer and fills in the place with

DNA nucleotides.

• DNA ligase links the two sections.

5. Describe the process of protein synthesis. (12.3; see Fig.15, p. 339)

6. Compare outcomes of mutations that occur in body-cells with those of mutations that occur in sex-cells. (12.4)

Mutations

Types of mutations• A permanent change that occurs in a cell’s DNA is called a

mutation.• Point mutation: involve chemical change to just one base pair

• Missense substitutions: DNA codes for the wrong amino acid• Nonsense mutation: Codon for amino acid becomes a stop

codon • Insertion/deletion: additions/ loss of a nucleotide to the DNA

sequence• Cause “frameshifts”

Mutations

Causes of mutation• Can occur spontaneously – DNA polymerase can attach the wrong

nucleotide, but this is rare and usually corrected.• Certain chemicals and radiation called mutagens can damage

DNA.• Chemicals can cause mispairing of base pairs, or themselves

substitute for base pairs.• High-energy radiation can eject electrons from atoms within

the DNA molecule, leaving behind unstable free radicals.

Mutations

Body-cell v. sex-cell mutation• Somatic cell mutations are not passed on to the next generation.• Mutations that occur in sex cells are passed on to the organism’s

offspring and will be present in every cell of the offspring.

7. What is endosymbiont theory? And, what is the evidence that supports this theory? (14.2)

Cellular Evolution

The endosymbiont theory• Lynn Margulis proposed the endosymbiont theory, which proposed

that ancestral eukaryotic cells absorbed prokaryotic cells, which evolved into organelles.

• Prokaryotes entered eukaryotic cells as undigested food or parasites.

• Their relationship became mutually beneficial.

• The theory explains the double membranes around mitochondria and chloroplasts.

8. Explain the four principles of the theory of natural selection. (15.1)

Developing the Theory of Evolution

Natural selection• Principles of natural selection:

• Individuals show variation

• Variations are heritable

• More offspring are born than can survive

• Variations that increase reproductive success will be more common in the next generation

9. There are five lines of evidence that support the scientific theory of evolution. List all five AND explain two of them. (15.2)

Support for Evolution• Evidence for evolution comes from:

• The fossil record

• Comparative anatomy

• Comparative embryology

• Comparative biochemistry

• Geographic distribution

Support for Evolution

The fossil record• Fossils show modern species resemble ancient species.

• They also reveal that some species have changed very little.

• The fossil record is an important source of information for determining the ancestry of organisms and the patterns of evolution.

Support for Evolution

The fossil record• Darwin predicted the existence of fossils intermediate in form

between species, such as Archaeopteryx.

• Researchers consider two major classes of traits when studying transitional fossils:

• Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors.

• Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.

Support for Evolution

Comparative anatomy• Anatomically similar structures inherited from a common ancestor

are called homologous structures.

• Evolution predicts that an organism’s body parts are more likely to be modifications of ancestral body parts than entirely new structures.

Support for Evolution

Comparative anatomy• Vestigial structures are structures that are the reduced forms of

functional structures in other organisms.

• Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost.

snake pelvis human appendix

Support for Evolution

Comparative anatomy• Analogous structures can be used for the same purpose and be

superficially similar in construction, but are not inherited from a common ancestor.

• Analogous structures show that functionally similar features can evolve independently under similar conditions.

Support for Evolution

Comparative embryology• An embryo is an early, pre-birth stage of an organism’s

development.

• Vertebrate embryos exhibit homologous structures during phases of development that become totally different structures in the adult forms.

The explanation for this similarity in embryos is a shared history of vertebrates—all vertebrates share a common ancestor that had a tailed embryo with gill pouches

Support for Evolution

Comparative biochemistry• Common ancestry can be seen in the complex metabolic molecules

that many different organisms share.

• The more closely related species are to each other, the greater the biochemical similarity.

Support for Evolution

Geographic distribution• The distribution of plants and animals that Darwin observed were

what first suggested evolution to him.

• The distribution of plants and animals around the world is studied in the field of biogeography.

• Evolution is linked to migration patterns, climate, and geological forces (such as plate tectonics).

10. Explain the concept of genetic drift. Include explanations of two specific types of genetic drift. (15.3)

Mechanisms of EvolutionPopulation genetics• For a population to be in genetic equilibrium (which means NOT

evolving) according to the Hardy-Weinberg principle, it must meet five conditions:1. No genetic drift2. No gene flow3. No mutation4. Mating must be random5. No natural selection

• These five conditions are the mechanisms of evolutionary change.

Mechanisms of EvolutionGenetic drift• Any change in the allelic frequencies in a population that results

from chance is called genetic drift. • In smaller populations, the effects of genetic drift become more

pronounced, and the chance of losing an allele becomes greater.

Mechanisms of EvolutionGenetic drift• The founder effect results when a group of individuals with a

different allele frequency than the original population becomes isolated. • Alleles that were infrequent in the original population may be

common in the new population.• Happens when a subset of organisms settles in an area

separated from their original population• Can result in large genetic variations in the separated

population

Mechanisms of EvolutionGenetic drift• A bottleneck results when population declines to a very low level

and then rebounds. • The gene pool of the rebound population is similar to the low-level

population, which may have reduced diversity.

11. Using binomial nomenclature, describe how scientific names are written. Give examples of scientific names for humans and for the Northern Cardinal. (17.1)

Early Systems of Classification

Linnaeus’s system• Linnaeus’s system of classification was based on observations of

morphology and habitat.

• The Linnaean system was the first formal system of taxonomy – the discipline of identifying, naming, and classifying organisms.

Binomial nomenclature• Linnaeus’s method of naming organisms, called binomial

nomenclature, gives each species a scientific name with two parts.

• The first part is the genus name, and the second part is the specific epithet, or specific name, that identifies the species.

• Biologists use scientific names for species because common names vary in their use.

Early Systems of Classification

Binomial nomenclature

• When writing a scientific name, scientists use these rules:

• The first letter of the genus name always is capitalized, but the rest of the genus name and all letters of the specific epithet are lowercase.

• If a scientific name is written in a printed book or magazine, it should be italicized.

• When a scientific name is written by hand, both parts of the name should be underlined.

• After the scientific name has been written completely, the genus name will be abbreviated to the first letter in later appearances (e.g., C. cardinalis).

12. Describe the hierarchical scheme for classifying organisms into taxonomic categories. (17.1)

Early Systems of Classification

Modern classification systems• Modern classification is rooted in the Linnaean system

• As the study of evolution grew, scientists began using evolutionary relationships in their classification systems.

Taxonomic Categories• The taxonomic categories used by

scientists are part of a nested-hierarchal system.

• Each category is contained within another, and they are arranged from broadest to most specific.

Taxonomic Categories

Species and genus• A named group of organisms is called a taxon.

• A genus is a group of species that are closely related and share a common ancestor.

Family• A family is the next higher taxon, consisting of similar, related

genera

Taxonomic Categories

Higher taxa• An order contains related families.

• A class contains related orders.

• A phylum or division contains related classes.

• A kingdom contains related phyla.

• The domain is the broadest of all the taxa and contains one or more kingdoms.

13. Explain how to construct a cladogram. You may sketch an example to go with your explanation (17.2)

Phylogenetic Reconstruction

Character types

• Cladistics classifies organisms based on the order that they diverged from a common ancestor.

• Scientists consider two main types of characters when doing cladistic analyses:

• Ancestral characters are found within the entire line of descent of a group of organisms.

• Derived characters are only found after a split from the descendent line.

Phylogenetic Reconstruction

Cladograms• A cladogram is a branching diagram that represents a proposed

phylogeny of a species or group.

• One branch of a cladogram is called a clade.

Phylogenetic Reconstruction

Cladograms• To construct a cladogram, groups

of interest need to be compared to an outgroup, which has more ancestral characteristics.

• The cladogram is constructed by sequencing the order in which derived characters evolved with respect to the outgroup.

• The more derived characteristics two groups share, the more recently the groups shared a common ancestor.

Diversity of Prokaryotes• Prokaryotes are divided into two domains: Bacteria and Archaea.

• Bacteria (eubacteria) belong to Domain Bacteria, exist in nearly every environment on earth, important to human body, industry, and food production.

• Archaea tolerate extreme environments, have similar proteins to eukaryotic cells.

14. Distinguish between Archaea and Bacteria. (18.1)

Diversity of Prokaryotes

Bacteria• Cell walls contain peptidoglycan

• Some have second cell walls

• Some are photosynthetic

Diversity of Prokaryotes

Archaea• Predominate in extreme environments

• Mostly anaerobic, cannot tolerate oxygen

• Include halophiles (salt-loving), methanogens (use CO2 and give off methane), and thermoacidiphiles (high temperature, low pH).

15. Why are viruses not considered part of the living world? (Lesson 13, 17.3, and 18.2)

Domain Eukarya

Viruses – an exception• A virus is a nucleic acid surrounded by a protein coat.• Viruses do not possess cells, nor are they cells, and are not

considered to be living.• Because they are nonliving, they usually are not placed in the

biological classification system.

16. Briefly describe each of the levels of biological organization found in a multicellular organism. (Lesson 25)

17. Briefly describe what processes occur in each of the following parts of the digestive system: mouth, stomach, small intestine, and the large intestine. (Lesson 27)

18. For plants, describe vascular tissue, and distinguish between the two types of vascular tissue. (Lesson 30)

19. The Russian olive tree (Elaeagnus angustifolia) is an exotic invasive tree capable of sexual reproduction. Sexual reproduction involves flowering, pollination, and production of fruit that has seeds within. This species is also capable of asexual reproduction. Briefly describe some of the different ways plants can reproduce asexually. (Lesson 31)

20. Pick any other topic we learned about this year and explain what your learned.