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Honors Biology Final Exam review
Adaptive Radiation
Definition: The rapid diversification of a single ancestral species into a wide variety of forms adapted to different environments or ecological niches.
Example: Darwin's finches in the Galápagos Islands, which evolved into different species with specialized beaks suited for various types of food sources.
Allopatric Speciation
Definition: Speciation that occurs when populations of a species become geographically isolated, leading to genetic divergence.
Example: A river that splits a population of squirrels, and over time, the two groups evolve into separate species due to lack of gene flow.
Barriers to Mating
Behavioral: Differences in mating behaviors or rituals that prevent interbreeding.
Example: Different bird species have distinct songs that attract only their species.
Geographic/Habitat: Physical separation between populations, like mountains or rivers, preventing interbreeding.
Example: A mountain range separating two populations of the same species.
Temporal: Species mate at different times of the year, preventing cross-breeding.
Example: Two species of frogs in the same area but one breeds in the spring and the other in the fall.
Mechanical: Differences in reproductive organs that prevent mating.
Example: Flowers with different shapes that only specific pollinators can access.
Gametic: Differences in the compatibility of sperm and egg cells between species.
Example: In some species of sea urchins, the sperm cannot fertilize the egg because of differences in surface proteins.
Cladogram
Definition: A diagram used to show relationships among species, based on shared derived characteristics (synapomorphies).
Derived Characteristics: Traits that are found in a species and its descendants, but not in its ancestors.
Coevolution
Definition: The process where two or more species influence each other's evolution, often in response to reciprocal selective pressures.
Example: The evolution of flowers and their pollinators, such as bees evolving to pollinate certain types of flowers.
Convergent Evolution
Definition: When unrelated species evolve similar traits due to similar environmental pressures.
Analogous Structures: Traits that have similar functions but arise from different evolutionary paths.
Example: The wings of bats and birds, both serve the function of flight but evolved independently.
Divergent Evolution
Definition: When two species with a common ancestor evolve different traits due to different environmental pressures.
Homologous Structures: Structures that are similar due to shared ancestry, even if they serve different functions.
Example: The forelimbs of humans, bats, and whales—though they have different functions, they share a common skeletal structure.
Evolution
Definition: The process by which populations of organisms change over generations through variations in traits and natural selection.
Extinction
Definition: The end of a species or group of species.
Micro or Macro?: Extinction is considered a form of macroevolution because it affects entire species or groups.
Fossil Record
Definition: The collection of preserved remains or traces of organisms from past geological ages.
Importance: Provides evidence of the history of life on Earth and the evolution of species.
Genetic Drift
Definition: Random changes in allele frequencies in a population, especially in small populations.
Example: A random event (like a natural disaster) drastically reducing a population's size, leading to genetic changes.
Genomics/DNA
Definition: The study of genomes, which are the complete set of DNA within an organism, including all its genes.
Geographic Isolation
Definition: Physical separation of populations that can lead to speciation.
Example: An island separating from a mainland population, leading to two distinct species over time.
Gradual Adaptation
Definition: Slow and steady changes in a species over time due to natural selection.
Hybridization
Definition: The process of interbreeding between two different species, often producing hybrid offspring.
Example: The mule, a hybrid of a horse and a donkey.
Macroevolution
Definition: Large-scale evolutionary changes that occur over geologic time, resulting in the formation of new species and higher taxonomic groups.
Mass Extinction
Definition: A widespread and rapid extinction of many species in a relatively short period of time.
Comparison to Background Extinction: Mass extinctions are more sudden and widespread compared to background extinctions, which occur gradually over time.
Current Mass Extinction: The sixth mass extinction is primarily caused by human activity (e.g., habitat destruction, climate change).
Microevolution
Definition: Small-scale evolutionary changes within a population, typically due to natural selection, genetic drift, or gene flow.
Migration/Gene Flow
Definition: The movement of genes between populations due to the migration of individuals, leading to changes in allele frequencies.
Mutations
Definition: Changes in the DNA sequence that can lead to new genetic variations.
Can Mutations Increase in a Population?: Yes, if they provide a selective advantage or are passed down through reproduction.
When Can Mutations Be Passed On?: Only if they occur in the gametes (sperm or eggs).
Are Mutations Always Harmful?: No, some mutations are neutral or even beneficial.
Natural/Artificial Selection
Natural Selection: The process by which organisms with traits better suited to their environment tend to survive and reproduce.
Artificial Selection: The human-driven process of selecting organisms with desired traits for breeding.
Example of Artificial Selection: Breeding dogs for specific traits like size or temperament.
Phenotype
Definition: The observable characteristics or traits of an organism, influenced by both its genotype and the environment.
Phylogenetic Tree
Definition: A diagram that shows the evolutionary relationships between species based on shared common ancestry.
Phylogeny
Definition: The evolutionary history and relationship of a species or group of species.
Population
Definition: A group of organisms of the same species living in the same area and capable of interbreeding.
Punctuated Equilibrium
Definition: A theory that suggests species remain relatively unchanged for long periods, punctuated by brief periods of rapid evolution.
Proposed by: Eldredge & Gould.
Reproductive Isolation
Definition: Barriers that prevent different species from interbreeding and producing viable offspring.
Speciation
Definition: The formation of new and distinct species due to factors like genetic divergence and reproductive isolation.
Two Main Drivers of Speciation:
Geographic Isolation (e.g., through geographic barriers)
Reproductive Isolation (e.g., different mating behaviors or times)
Species
Definition: A group of organisms that can interbreed and produce fertile offspring.
Sympatric Species
Definition: Species that live in the same geographic area but avoid interbreeding due to other forms of reproductive isolation.
Taxonomy
Linnaeus: Developed the binomial nomenclature system for naming species.
Proper Naming: Species names should be italicized, with the genus capitalized and the species lowercase (e.g., Homo sapiens).
The Six Kingdoms:
Animalia, Plantae, Fungi, Protista, Archaea, Bacteria
Three Domains:
Eukarya, Archaea, Bacteria
Temporal Isolation
Definition: Species that reproduce at different times, preventing interbreeding.
Example: Two species of frogs breeding in different seasons.
Three Major Sources of Changes in Allele Frequency:
Mutations: Random genetic changes that introduce new alleles.
Gene Flow: The movement of alleles between populations through migration.
Genetic Drift: Random changes in allele frequency, especially in small populations.
Important Terminology to Know
Bacteriophage (phage): A virus that infects bacteria. Important in studies of genetic material transmission.
Base pairing rules (complementary pairing): The principle that adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G) in DNA.
DNA polymerase: Enzyme that adds complementary nucleotides to a growing DNA strand during replication. It also checks for mistakes and corrects them.
Double helix: The twisted ladder structure of DNA, formed by two complementary strands of nucleotides.
Helicase: An enzyme that unwinds the DNA double helix ahead of the replication fork.
Lagging strand: The DNA strand that is replicated in small segments (Okazaki fragments) in the direction opposite to the replication fork.
Leading strand: The DNA strand that is synthesized continuously in the direction of the replication fork.
Nucleotide: The monomer unit of DNA, consisting of a phosphate group, a sugar (deoxyribose), and a nitrogenous base (A, T, C, or G).
Okazaki fragments: Short DNA fragments formed on the lagging strand during DNA replication.
Purine: A type of nitrogenous base that has a two-ring structure. Examples: adenine (A) and guanine (G).
Pyrimidine: A type of nitrogenous base with a single ring. Examples: cytosine (C) and thymine (T).
Replication: The process by which DNA makes a copy of itself.
Replication origins (bubbles): Sites where DNA replication begins; the DNA is unwound into a bubble-like structure.
Semiconservative replication: A model of DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.
Key People in DNA Research
Frederick Griffith: Discovered the process of bacterial transformation using Streptococcus pneumoniae.
Oswald Avery: Showed that DNA is the substance responsible for transformation, not proteins.
Martha Hershey and Alfred Chase: Conducted the famous experiment with bacteriophages to demonstrate that DNA, not protein, is the genetic material.
Rosalind Franklin & Maurice Wilkins: Used X-ray crystallography to capture images of DNA, leading to the understanding of its double helix structure.
James Watson & Francis Crick: Proposed the double-helix model of DNA, integrating Franklin’s X-ray data.
Erwin Chargaff: Discovered that the amount of adenine equals thymine, and the amount of cytosine equals guanine in a DNA molecule (Chargaff’s rules).
General DNA Composition and Structure
What two things does a chromosome consist of?
DNA
Proteins (mainly histones)
What did scientists believe was the molecule of inheritance before DNA was discovered? Most scientists believed proteins were the molecule of inheritance because of their complexity and diversity compared to DNA, which was thought to be too simple.
What is the monomer of DNA? A nucleotide, consisting of:
A phosphate group
A deoxyribose sugar
A nitrogenous base (A, T, C, or G)
What part of the nucleotide varies between the 4 nucleotides? The nitrogenous base is what varies.
Bonding in DNA:
Phosphate and sugar bonds (phosphodiester bonds): These form the backbone of the DNA strand, and they are strong bonds.
Base pairing (hydrogen bonds): These form between the complementary nitrogen bases (A-T, C-G) and are weak bonds, which is important for DNA to be easily unwound and replicated.
Purines vs Pyrimidines:
Purines: Adenine (A) and Guanine (G), have two rings in their structure.
Pyrimidines: Cytosine (C) and Thymine (T), have one ring in their structure.
Base Pairing: A pairs with T (2 hydrogen bonds) and C pairs with G (3 hydrogen bonds).
DNA Replication
When does DNA replication occur? During S-phase of the cell cycle (Synthesis phase of Interphase).
Where does DNA replication occur in eukaryotic cells? In the nucleus.
Why does DNA replication occur? So that each daughter cell receives an exact copy of the genetic material.
Key players in DNA replication:
Helicase: Unwinds the DNA double helix.
Single-strand binding proteins (SSBs): Keep the single-stranded DNA stable and prevent it from re-annealing.
DNA polymerase: Adds complementary nucleotides to the growing DNA strand. It also has proofreading capabilities.
Primase: Adds a short RNA primer so DNA polymerase can begin replication.
Ligase: Joins Okazaki fragments on the lagging strand.
Leading strand: Synthesized continuously in the direction of the replication fork.
Lagging strand: Synthesized in fragments (Okazaki fragments) because it’s replicated in the opposite direction to the replication fork.
Why is replication semi-conservative? Because each of the two new DNA molecules consists of one old strand and one new strand.
DNA and RNA Basics
Primary functions of DNA:
Stores genetic information.
Directs the synthesis of proteins.
Complementary bases in DNA:
A pairs with T.
C pairs with G.
Monomer of RNA: A nucleotide, which is similar to DNA but contains ribose instead of deoxyribose, and has uracil (U) instead of thymine (T).
Differences between DNA and RNA:
Sugar: DNA has deoxyribose; RNA has ribose.
Base: DNA has thymine (T), RNA has uracil (U).
Strands: DNA is double-stranded; RNA is single-stranded.
Protein Synthesis Process
Transcription: The process of copying the DNA code onto mRNA. It occurs in the nucleus.
Translation: The process of using mRNA to build a protein at the ribosome in the cytoplasm.
Codon: A set of 3 mRNA nucleotides that codes for a specific amino acid.
tRNA: Transfers amino acids to the ribosome based on the mRNA codon sequence.
rRNA: Makes up the structure of the ribosome.
Splicing: The process of removing introns and joining exons in pre-mRNA to form mature mRNA. It occurs in the nucleus. Introns are removed, exons stay in the nucleus and are expressed.
Translation:
mRNA carries the genetic code from DNA to the ribosome.
tRNA matches its anticodon with mRNA codons, bringing the correct amino acid.
The ribosome forms peptide bonds between amino acids to create the protein.
Mutations
Point mutations (substitutions, insertions, deletions) can change the sequence of amino acids in a protein, potentially altering its function.
Silent mutation: No effect on the protein.
Missense mutation: A single amino acid is changed.
Nonsense mutation: The change creates a stop codon, shortening the protein.
Frameshift mutation: Insertion or deletion of nucleotides shifts the reading frame, potentially altering every subsequent amino acid.
Example Sequence to Complete
Given the DNA coding strand:
TAC TCC CCG GAG AAT GTC CTA TCC GGC ATC
mRNA codons:
AUG AGG GGC CUC UUA CAG GAU AGG CCG UAG
Amino acids:
Methionine (Met) - Arginine (Arg) - Glycine (Gly) - Leucine (Leu) - Glutamine (Gln) - Aspartate (Asp) - Arginine (Arg) - Proline (Pro) - Stop
Sure! Here’s an overview of the specific jobs and processes that lead to the formation of DNA and RNA:
DNA (Deoxyribonucleic Acid)
Job/Function:
Storage of Genetic Information: DNA serves as the blueprint for all living organisms. It contains the instructions needed for the development, functioning, growth, and reproduction of all cells.
Cell Division: DNA ensures that genetic information is passed accurately during cell division, ensuring that offspring cells inherit the correct genetic material.
Formation/Process:
DNA Replication: The process by which DNA makes an identical copy of itself before cell division. This occurs during the S phase of the cell cycle.
Steps:
Unwinding: The double helix of DNA unwinds with the help of enzymes like helicase.
Base Pairing: DNA polymerase adds complementary nucleotides to each original strand (template strand) to form new strands.
Proofreading: DNA polymerase also checks for errors and corrects them to ensure accuracy.
End result: Two identical DNA molecules are produced, each consisting of one old strand and one new strand (semiconservative replication).
RNA (Ribonucleic Acid)
Job/Function:
Protein Synthesis: RNA plays a crucial role in converting genetic information from DNA into proteins, which are essential for various cellular functions.
Messenger RNA (mRNA) carries the genetic code from DNA to the ribosome for protein synthesis.
Transfer RNA (tRNA) helps in translating the mRNA code into a sequence of amino acids to form proteins.
Ribosomal RNA (rRNA) forms the structure of ribosomes and aids in protein synthesis.
Formation/Process:
Transcription: This is the process by which an RNA molecule is synthesized from a DNA template.
Steps:
Initiation: RNA polymerase binds to a specific region of the DNA (the promoter) to start transcription.
Elongation: RNA polymerase moves along the DNA template strand and synthesizes the RNA strand, adding RNA nucleotides that are complementary to the DNA sequence.
Termination: The RNA polymerase reaches a termination signal, and the RNA molecule is released.
End result: The RNA transcript (mRNA) is formed and can then be processed and used in translation.
Comparison in the Context of Protein Synthesis:
DNA contains the genetic information that codes for proteins but cannot directly participate in protein synthesis. It stays in the nucleus of eukaryotic cells to protect the genetic code.
RNA acts as the intermediary between DNA and proteins:
mRNA is transcribed from DNA and carries the code for protein synthesis to the ribosome.
tRNA helps translate this code into a specific sequence of amino acids, forming proteins.
rRNA is a structural component of the ribosome, facilitating the assembly of amino acids into proteins.
Blending Hypothesis: An outdated theory suggesting that offspring are a "blend" of the traits of their parents. This was later disproved by Mendel's work, which showed traits are inherited discreetly.
Particulate Hypothesis: Mendel’s theory that genes are inherited as discrete units (alleles) that do not blend but are passed down intact.
Traits: Characteristics that are inherited, such as eye color or height.
Genetics: The study of heredity and the variation of inherited characteristics.
Purebred (True Breeding): Organisms that, when self-fertilized, produce offspring that are identical to the parent in terms of a particular trait (homozygous for that trait).
Cross: Mating of two organisms to observe inheritance patterns in their offspring.
Cross Fertilization (Cross Pollination): Fertilization between two different plants (or organisms) with different genetic traits.
Self-Fertilization (Self-Pollination): When a plant (or organism) fertilizes itself, typically with its own pollen.
Locus: The specific physical location of a gene on a chromosome.
Gene: A segment of DNA that encodes for a specific protein or trait.
Allele: Different forms of a gene. For example, a gene for flower color might have alleles for red and white. Represented in a genotype as letters: dominant allele (capital letter) and recessive allele (lowercase letter).
Homozygous: An organism that has two identical alleles for a particular trait (e.g., AA or aa).
Heterozygous: An organism that has two different alleles for a particular trait (e.g., Aa).
Genome: The complete set of genes or genetic material present in an organism.
Genotype: The genetic makeup of an organism, specifically the alleles inherited from both parents (e.g., Aa, BB).
Phenotype: The physical expression or appearance of a trait (e.g., red flowers, tall plants).
Dominant: An allele that expresses its effect even when only one copy is present in the genotype (heterozygous). Dominant alleles are often represented with a capital letter (e.g., "A"). Misconception: Dominant does not necessarily mean "better" or more common.
Recessive: An allele that expresses its effect only when two copies are present (homozygous). Represented with a lowercase letter (e.g., "a"). Can be expressed only when the individual is homozygous recessive (aa).
Punnett Square: A diagram used to predict the genetic outcomes of a cross between two organisms.
Monohybrid Cross: A genetic cross between two organisms involving one trait (e.g., flower color).
Testcross: A cross between an organism with an unknown genotype and a homozygous recessive individual to determine the unknown genotype.
Dihybrid Cross: A cross between two organisms involving two traits (e.g., seed color and seed shape).
Probability: The likelihood of a particular genetic outcome occurring, often expressed as a percentage or ratio.
Crossing Over: The exchange of genetic material between homologous chromosomes during prophase I of meiosis, increasing genetic variation.
Random Fertilization: The random combination of gametes (sperm and egg) during fertilization, contributing to genetic variation.
Independent Assortment: The principle that genes for different traits are inherited independently of one another (Mendel’s Law of Independent Assortment).
Genetic Linkage: Genes that are close together on the same chromosome are more likely to be inherited together, violating the Law of Independent Assortment.
Law of Segregation: Mendel's law stating that alleles separate during gamete formation, and each gamete carries only one allele for each trait.
Carrier: An individual who carries one copy of a recessive allele for a genetic disorder but does not express the disorder themselves. Women are more likely to be carriers of X-linked recessive disorders due to having two X chromosomes (e.g., color blindness, hemophilia).
Sex-Linked Genes: Genes located on sex chromosomes (X or Y). X-linked genes are more likely to be expressed in males because they have only one X chromosome (XY), whereas females have two X chromosomes (XX), so the second X can mask a recessive trait.
Autosomes: Chromosomes that are not sex chromosomes (chromosomes 1-22 in humans).
Sex Chromosomes: Chromosomes that determine the sex of an individual (X and Y chromosomes).
Incomplete Dominance: A form of inheritance where the heterozygous phenotype is a blend of the two homozygous phenotypes (e.g., red + white = pink flowers).
Codominance: A form of inheritance where both alleles are equally expressed in the heterozygous phenotype (e.g., a cow with both red and white patches).
Polygenic Traits: Traits that are influenced by multiple genes, often resulting in a continuous range of phenotypes (e.g., skin color, height).
Linkage Maps: Diagrams showing the relative positions of genes on a chromosome. Thomas Hunt Morgan is credited with developing linkage maps.
Pedigree: A family tree diagram used to track inheritance patterns of traits through generations. Squares represent males, circles represent females, and shaded shapes represent individuals expressing the trait.
Karyotype: A photographic representation of an individual's chromosomes, arranged in pairs. Disorders such as Down syndrome (trisomy 21) can be detected by examining a karyotype.
P, F1, & F2:
P: Parental generation (original cross).
F1: First filial generation (offspring from the P generation).
F2: Second filial generation (offspring from the F1 generation).
XX Sex Chromosomes: Female genotype (female gender).
XY Sex Chromosomes: Male genotype (male gender).
Important Individuals in Genetics
Gregor Mendel: Father of genetics, conducted experiments with pea plants and formulated the Laws of Inheritance (Law of Segregation and Law of Independent Assortment).
Thomas Hunt Morgan: A pioneering geneticist who worked with fruit flies and discovered the concept of sex-linked inheritance and genetic linkage.
Reginald C. Punnett: Co-developed the Punnett square for predicting genetic outcomes and worked on the study of genetic inheritance in pea plants.
Mendel’s Pea Plant Experiment:
Mendel’s experiment involved cross breeding pea plants that differed in traits such as flower color, seed shape, and plant height. By examining the ratios of traits in the F1 and F2 generations, he concluded that traits are inherited as discrete units (genes), and each parent contributes one allele for each trait to their offspring. He established the concepts of dominant and recessive alleles and the laws of inheritance.
Genetic Variation and Meiosis:
Crossing over occurs during prophase I of meiosis, resulting in new combinations of alleles on chromosomes.
Independent assortment occurs during metaphase I of meiosis, where homologous chromosomes are randomly distributed to gametes, increasing variation.
Random fertilization occurs when any sperm can fertilize an egg, further increasing genetic variation.
Inheritance Patterns
Complete Dominance: One allele completely masks the expression of the other (e.g., TT = tall, Tt = tall, tt = short).
Incomplete Dominance: The heterozygote exhibits a blend of the two alleles (e.g., red + white = pink flowers).
Codominance: Both alleles are fully expressed in the heterozygote (e.g., red + white = red and white stripes).
Dihybrid Cross: Involves two traits (e.g., seed color and seed shape), requiring a 16-box Punnett square.
Multiple Alleles: More than two alleles exist for a gene (e.g., ABO blood types).
Sex-Linked Inheritance: Traits controlled by genes located on sex chromosomes, often X-linked, such as color blindness or hemophilia.
Polygenic Inheritance: Traits controlled by multiple genes, often resulting in a range of phenotypes (e.g., height, skin color).
Environmental Effects: The environment can influence the expression of genes (e.g., temperature-sensitive fur color in Siamese cats).
Testcross
A testcross is used to determine the genotype of an individual expressing a dominant trait. If the individual is homozygous dominant, all offspring will express the dominant trait. If heterozygous, about half will express the recessive trait.
Practice Problems:
Punnett Squares: Be able to set up Punnett squares for all types of inheritance (monohybrid, dihybrid, incomplete dominance, codominance, etc.) and calculate genotype and phenotype probabilities.
Key Concepts and Definitions
1. Species Are Fixed
The belief that species do not change over time. This was the prevailing thought before Darwin’s theory of evolution.
2. Adaptations
Traits that increase an organism's chances of survival and reproduction in a particular environment.
3. Allele Frequency
The proportion of a particular allele among all allele copies in a population.
4. Analogous Structures
Structures in different species that perform the same function but do not have a common evolutionary origin.
Example: Wings of birds and insects.
5. Artificial Selection
Humans intentionally breed organisms with desirable traits.
Example: All dog breeds came from wolves through artificial selection.
6. Binomial Nomenclature
A system for naming species using two names: the genus and species (specific epithet).
Example: Homo sapiens (genus: Homo, species: sapiens).
7. Biogeography
Study of the geographic distribution of species. It provides evidence for evolution by showing how
species are adapted to their environments.
8. Bottleneck Effect
A reduction in genetic diversity due to a drastic decrease in population size, often caused by a catastrophe.
9. Catastrophism
The idea that Earth’s history has been shaped by sudden, short-lived, and violent events, such as natural disasters.
Proposed by: Georges Cuvier.
10. Cladogram
A diagram used to show the relationships among species based on shared traits.
11. Directional Selection
Natural selection that favors one extreme phenotype over others.
Example: Giraffes with longer necks are favored.
12. Disruptive Selection
Natural selection that favors both extreme phenotypes and eliminates intermediate phenotypes.
Example: Birds with either very small or very large beaks are favored.
13. Evolution
A change in the genetic makeup of a population over time. Evolution occurs at the population level.
14. Fitness
The ability of an organism to survive and reproduce. It is measured by how many offspring an individual leaves in the next generation.
15. Fossils
Remains or traces of ancient organisms preserved in rocks. Fossils provide evidence of evolutionary changes over time.
16. Founder Effect
A reduction in genetic variation when a small group of individuals starts a new population.
Example: A few individuals from a large population colonize an isolated island.
17. Gene Flow
The transfer of genetic material between populations through migration or interbreeding.
18. Gene Pool
The total genetic diversity found within a population.
19. Genetic Drift
A random change in allele frequencies in a small population, often due to chance events.
20. Genus
A classification category that ranks above species and below family.
Example: Homo (genus for humans).
21. Hardy-Weinberg Equilibrium
A model used to measure genetic changes in a population over time. Five conditions for equilibrium:
No mutations
Random mating
No natural selection
Large population size
No gene flow
Formula: p² + 2pq + q² = 1
22. Heritability
The proportion of variation in a trait that can be attributed to genetic differences.
23. Homologous Structures
Structures that have a common evolutionary origin, even if they serve different functions.
Example: The forelimbs of humans, bats, and whales.
24. Hybridization
The process of breeding two different species to create hybrid offspring.
Example: Mule (horse + donkey).
25. Inheritance of Acquired Characteristics
Lamarck’s discredited idea that traits acquired during an organism’s lifetime can be passed onto offspring.
Example: Lamarck suggested that giraffes’ long necks evolved because they stretched to reach higher leaves.
26. Interspecific Variation
Variation between different species.
27. Intraspecific Variation
Variation within the same species.
28. Microevolution
Small-scale changes in allele frequencies in a population over time.
29. Migration
Movement of individuals between populations, contributing to gene flow.
30. Mutation
A change in the DNA sequence. Mutations can create new alleles and contribute to genetic variation.
31. Natural Selection
The process by which individuals with beneficial traits are more likely to survive and reproduce. It is a key mechanism of evolution.
32. Normal Distribution
A bell-shaped curve that represents the distribution of traits in a population. Most individuals have average traits, with fewer having extreme traits.
33. Paleontology
The study of fossils and ancient life forms.
34. Phenotype
The observable physical traits of an organism.
35. Population
A group of individuals of the same species living in the same area.
36. Recombination
The process during meiosis that shuffles genes and creates genetic variation.
37. Species
A group of organisms that can interbreed and produce fertile offspring.
38. Specific Epithet
The second part of a species name in binomial nomenclature, unique to each species within a genus.
39. Stabilizing Selection
Natural selection that favors the average phenotype and reduces variation.
Example: Human birth weight, where extremes are less common.
40. Uniformitarianism
The idea that Earth’s features are shaped by continuous, uniform processes like erosion, proposed by James Hutton.
41. Variation
Differences in traits among individuals in a population.
42. Vestigial Structures
Structures that have lost their original function.
Example: Human appendix or whale pelvic bones.
People and Their Contributions to Evolution
1. Carolus Linnaeus
Developed binomial nomenclature and classified organisms.
2. Georges de Buffon
Proposed that species change over time and may have common ancestors.
3. Erasmus Darwin
Suggested that life evolved from a common ancestor.
4. Jean Baptiste Lamarck
Proposed the idea of inheritance of acquired characteristics.
5. George Cuvier
Advocated for catastrophism and believed that extinction had occurred.
6. James Hutton
Proposed the idea of uniformitarianism, suggesting that geological processes occur gradually over time.
7. Charles Lyell
Supported Hutton’s ideas and applied them to the understanding of Earth's geological history.
8. Thomas Malthus
Proposed that populations grow exponentially, leading to competition for limited resources.
9. Alfred Russel Wallace
Developed a theory of evolution by natural selection similar to Darwin’s.
Darwin’s Observations and Ideas
Variation: Individuals in populations vary.
Struggle for Existence: Organisms produce more offspring than can survive, leading to competition.
Survival of the Fittest: Organisms with advantageous traits are more likely to survive and reproduce.
Adaptation: Over time, favorable traits become more common in a population.
Common Descent: All species are related by common ancestry.
Darwin’s Theory of Evolution by Natural Selection
Mechanism: Natural selection works on heritable traits, acting on individuals.
Inheritance: Traits passed from parents to offspring (genes).
Variation: Variation exists due to mutations, recombination, and gene flow.
Fitness: Those with advantageous traits survive and reproduce more, passing on their genes.
Adaptations: Traits that increase survival and reproduction in a specific environment.