Biology Chapter 5: Genetics and Classification

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Questions and Answers

What effect does gene flow have on a population?

It increases genetic variation in the population. (correct)

It decreases the number of intermediate phenotypes.

It reduces genetic variation within the population.

It stabilizes the genetic traits of the population.

Which statement best describes natural selection?

It focuses on random mating within a population.

It favors organisms with traits best suited for survival. (correct)

It allows all traits to survive regardless of environmental factors.

It ensures that offspring inherit all traits equally.

Which blood group genotype(s) possess the A antigen?

IAIO (correct)

IAIA (correct)

IBIB

I OI O

Which is the largest and most inclusive group in the Linnaean system of classification?

Kingdom Signup and view all the answers

What type of inheritance occurs when both alleles are expressed equally in the phenotype of heterozygotes?

Codominance Signup and view all the answers

What is binomial nomenclature?

A two-word naming system using Latin for genus and species. Signup and view all the answers

Who is known as the 'father of taxonomy'?

Carl Linnaeus Signup and view all the answers

Which blood group has no antigens present on the red blood cells?

Type O Signup and view all the answers

What is the smallest and most exclusive grouping in the Linnaean system?

Species Signup and view all the answers

In terms of dominance, how are the A and B alleles related to the O allele?

A and B are dominant to O Signup and view all the answers

Which of the following best describes systems of classification?

An organized method of arranging organisms based on natural relationships. Signup and view all the answers

What is a characteristic of polygenic traits?

Influenced by multiple genes Signup and view all the answers

What phenotype results from incomplete dominance between two alleles?

An intermediate phenotype Signup and view all the answers

Which of the following statements about gene flow is false?

Gene flow has no impact on population variations. Signup and view all the answers

Which ABO genotype corresponds to type B blood?

IBIB Signup and view all the answers

What defines codominance in blood types?

Both A and B alleles are expressed Signup and view all the answers

What is the primary limitation of the biological species concept?

It excludes extinct species and asexual organisms. Signup and view all the answers

Which species concept is based on the idea of organisms sharing distinct characteristics?

Typological/morphological species concept Signup and view all the answers

Which of the following groups of organisms can interbreed and produce fertile offspring according to the biological species concept?

Only organisms belonging to sexual reproduction species Signup and view all the answers

What defines the evolutionary species concept?

A species is a lineage of ancestor-descendant populations. Signup and view all the answers

What is a characteristic of the typological/morphological species concept according to Aristotle?

Species are seen as unchanging and distinct groups. Signup and view all the answers

Which example illustrates organisms that look similar but belong to different species?

Cactus and Euphorbia Signup and view all the answers

Which of the following statements is true regarding species that reproduce asexually?

They are excluded from the biological species concept. Signup and view all the answers

How do evolutionary biologists define a species according to their concept?

A lineage of populations with distinct identities. Signup and view all the answers

Study Notes

DNA Structure and Properties

DNA is the hereditary material in humans and almost all other organisms
It carries the genetic material of an organism
Most DNA is located in the cell nucleus, but a small amount is found in mitochondria (mitochondrial DNA) and chloroplasts
The components of a nucleotide include a phosphate group, a pentose sugar (deoxyribose), and a nitrogenous base

Components of a Nucleotide

Phosphate group: A phosphorus atom bonded with four oxygen atoms
Pentose sugar (deoxyribose): A five-carbon sugar
Nitrogenous base: A nitrogen-containing molecule; can be classified as either a purine (adenine, guanine) or a pyrimidine (thymine, cytosine)

The Nitrogenous Bases (DNA)

Classified into two groups
- Pyrimidines: Thymine and Cytosine
- Purines: Adenine and Guanine
Adenine pairs with Thymine (2 hydrogen bonds)
Guanine pairs with Cytosine (3 hydrogen bonds)

Salient Features of the Double-Helix Structure of DNA

Composed of two polynucleotide chains
Backbone is formed by sugar-phosphate units
Bases project inwards
Chains have anti-parallel polarity (5' to 3' and 3' to 5')

DNA Replication

The process of producing two identical replicas from one original DNA molecule
DNA replication is semi-conservative
Each newly synthesized molecule contains one original "parent template" strand and one new "daughter" strand

Key Enzymes in DNA Replication

Helicase: Unwinds the DNA double helix
Primase: Provides the starting point of RNA
DNA Polymerase: Adds new nucleotides to the 3' end of the elongating strand. It also proofreads and corrects errors.
DNA Ligase: Re-anneals the semi-conservative strands and joins Okazaki fragments of the lagging strands
Topoisomerase: Relaxes the supercoiled nature of the DNA
Single-strand Binding Proteins (SSBs): Bind to ssDNA to prevent re-annealing after DNA helicase unwinds, maintaining strand separation

The Central Dogma of Molecular Biology

A theory stating that genetic information flows in one direction from DNA to RNA to protein
The steps of the process involve Replication, Transcription, and Translation

Transcription

The process of synthesizing mRNA from DNA
Involves the transfer of the DNA code to mRNA within the nucleus

Translation

The process of reading the RNA sequence of an mRNA to create the amino acid sequence of a protein

Variations

Naturally occurring genetic differences among individuals of the same species

Mendel's Laws of Inheritance

Mendel's First Law (Law of Dominance): In a heterozygote, one trait will conceal another trait for the same characteristic.
Mendel's Second Law (Law of Segregation): Alleles segregate from each other during gamete formation (meiosis) such that only one allele is present in each gamete.
Mendel's Third Law (Law of Independent Assortment): Alleles of different genes are sorted independently into gametes.
Monohybrid Cross: A cross between individuals heterozygous for a single trait (e.g., monohybrid cross for flower color).
Dihybrid Cross: A cross between individuals heterozygous for two traits (e.g., dihybrid cross for seed color and seed shape).

Non-Mendelian Patterns of Inheritance

Multiple Alleles: A single gene with more than two normal versions (e.g., ABO blood groups)
Codominance: Both alleles for a gene are expressed equally in the phenotype (eg. AB blood type).
Incomplete Dominance: The dominant allele is not completely dominant over the recessive allele; the resultant phenotype is intermediate (eg. pink flowers)
Polygenic Traits: Traits controlled by more than one gene, with the alleles of each gene having a small additive effect on the phenotype (eg. human height).
Pleiotropy: A single gene that affects multiple phenotypic traits.
Epistasis: One gene influences/affects the expression of one or more other genes.

Earth's Origin

Earth formed approximately 4.6 billion years ago
Early Earth conditions were extremely harsh
- Constant bombardment from space debris
- Extremely high temperatures
- Toxic atmosphere (containing nitrogen oxides, methane, ammonia, and hydrogen sulfide) without much oxygen
- Frequent volcanic eruptions
- Intense lightning and radiation

Geologic Time Scale

The geologic time scale (GTS) is a record of Earth's history and the order of life from 2500 Mya to the present
It divides Earth's history into eons, eras, periods, and epochs
The divisions are based on changes in life-forms over time

Early Invertebrates

Cambrian Period (488-444mya) and Ordovician Period (448-444mya)
- Brachiopods, anomalocaris, pikaia gracilens were abundant
The Ordovician period saw the appearance of many animals with jointed external skeletons, known as arthropods

Early Coral Reefs, Fishes, Vascular Plants

Silurian Period (444-416 mya)
- Jawless fish, first known freshwater fish, vascular plants (Cooksonia)
Devonian Period (416-359 mya)
- Placoderms (armored fishes), bony fishes (ray-finned fishes), lobe-finned fish, early vascular plants, lycophytes, horsetails, ferns
- First tetrapods (four-limbed vertebrates) and insects

Amphibians, Origins of Reptiles, First Seed Plants

Carboniferous Period (359-299 mya):
- vast swamp forests, ferns, lycophytes, early amphibians, earliest reptiles

Reptiles (Dinosaurs), First Angiosperms, First Mammals

Mesozoic Era (251-65.5 mya), Triassic, Jurassic, and Cretaceous Periods
- Marine reptiles, dinosaurs, first angiosperms (flowering plants), first mammals

Mammals

Cenozoic Era (65.5 -present)
- First primates, rodents, apes, and humans

Evolution

The change in heritable characteristics of biological populations over successive generations
Natural selection is a key mechanism of evolution

Evidence of Evolution

Direct (fossils):
- Fossils provide a record of how organisms have changed over time
Indirect evidence:
- Comparative Anatomy
  - Homologous structures, analogous structures, vestigial structures
- Molecular Biology
  - Examining the similarities of biochemical molecules (DNA, ATP, amino acids, enzymes)
- Biogeography
  - Studying the distribution of organisms
- Embryological Development
  - Examining the similarities in the embryonic development of various organisms

How evolution or change in gene pool occurs

Nonrandom mating
Mutation, changes in gene and chromosome composition
Genetic drift, change in gene pool due to chance alone
Gene flow, when individuals migrate from one population to another

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Description

Test your knowledge on genetics and classification concepts with this quiz focusing on natural selection, blood group inheritance, and Linnaean taxonomy. Questions cover key principles like gene flow, codominance, and patterns of inheritance. Perfect for students looking to review important biological concepts.