IB Bio HL Unit 2

Morphological species concept

Classifies organisms into distinct species based on shared physical traits such as size, shape, and color

Biological species concept

Defines a species as a group of populations whose members can successfully interbreed in nature and produce viable, fertile offspring, while being reproductively isolated from other groups

Binomial nomenclature

Species named using genus & species names, genus name comes first & first letter is capitalized, species name in lowercase

Genome

All of the genetic information of an organism

Single-nucleotide polymorphisms (SNPs)

Replacement of a single nucleotide with another, producing variation within a species. These are often found in non-coding regions of DNA

Haploid

Haploid cells possess only one chromosome from each homologous pair

Diploid

A cell or organism with two complete sets of chromosomes, one from each parent

How do you calculate chromosome number

Number of human chromosomes

46 (diploid)

Number of chimpanzee chromosomes

48 (diploid)

Chromosome fusion

The event where parts of a different chromosomes break and rejoin, creating a new, longer chromosome or resulting in a fusion gene

Which chimpanzee chromosomes fused to make which human chromosome

Chimpanzee chromosomes 12 & 13 fused to create chromosome 2 in the human karyotype

Karyogram 

The image created by sorting, matching, and aligning the chromosomes of an individual allowing for the visual interpretation of the chromosome characteristics 

Karyotype

Actual complete set of an individual’s chromosomes, including their number, size, shape, and banding patterns

Aneuploidy

A condition where cells or an organism has an abnormal number of chromosomes, either one or more extra or missing

Monosomy

A genetic condition where an individual is missing one copy of a chromosome pair

Trisomy

A genetic condition where an individual has three copies of a particular chromosome instead of the usual two 

Trisomy 21

A genetic disorder caused by an extra copy of chromosome 21 (Down syndrome)

Chromosomes

Thread-like structures within cells that carry genetic information in the form of DNA, organized into genes that determine physical traits and guide cell development

Homologous chromosomes

Matched pairs of chromosomes in diploid organisms, with one chromosome inherited from each parent

Autosomes

Chromosomes that do not play a role in determining the sex of an organism

Sex chromosomes

A specific pair of chromosomes that determine the sex of an individual

XX

Female

XY

Male

Why aren’t sex chromosomes homologous chromosomes

Homologous chromosomes are nearly identical in size, shape, and gene content, and X & Y chromosomes are very different in size and genetic content The

Locus/loci

The specific, fixed physical location of a gene on a chromosome

Alleles

Alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

Dichotomous key

Tool used in fieldwork to aid in identification of organisms, composed of a series of questions or statements based on the physical characteristics of the organisms concerned

Sexual reproduction

Involves two parents, results in genetically unique offspring (fusion of gametes, such as sperm & egg to form a zygote)

Asexual reproduction

Produces genetically identical offspring from a single parent (ex: binary fission, budding)

Bacterial conjugation

A process in which bacteria transfer genetic material, such as plasmids between cells through direct contact

Horizontal gene transfer

Genetic material is exchanged between individuals rather than passed on from one generation to the next

Linnaeus

Swedish naturalist who came up with morphological species concept

Where does morphological species concept fall short

Some species look so similar it can be hard to distinguish between them, some species have sexual dimorphism (males and females have very different characteristics)

Where does biological species concept fall short

Concept cannot be applied to organisms that reproduce asexually, not a strict biological rule, competing definitions of what a species is, remains debatable 

How to calculate chromosome number

Through karyotyping, which involves counting the visible chromosomes in a sample of cells