IB Bio HL Unit 2 - Evolution and Classification

Evolution

The gradual process by which the inherited traits of populations change over many generations.

Speciation

The process by which new and distinct species evolve from a single ancestral lineage, often through mechanisms of reproductive isolation.

Karyotype

A full set of chromosomes in order based on size, number, type, etc.

Karyogram

An image or diagram of the karyotypes chromosomes

Karyotyping

The process of examining an organism's chromosomes by arranging them in homologous pairs to identify any abnormalities in their number or structure.

Dichotomous key

A classification tool that uses a series of paired statements, or "choices", to progressively narrow down the possibilities until an unknown organism is identified. Basically used as a matching game map organizer.

Sexual reproduction

• crossing over

• random assortment of chromosomes

Asexual reproduction

• genetically identical to the original organism

• variation increases slightly due to mistakes in the DNA replication process.

Linnaeus

Came up with the classification system we use today. He made two-part names (binomial nomenclature) and hierarchical classification.

Morphological Species concept

The classification of organisms into the species based upon shared morphological (physical) characteristics.

Biological species concept

Defines a species as a group of naturally interbreeding populations that are reproductively isolated from other groups.

Binomial Nomenclature

Two-part name of species. First part is the genus, second part is the specific epithet which is unique for each species. These names are necessary because they give us info about relationships between organisms closely related organisms will share the same genus, an they create a universal language to talk about organisms.

Genome

All the genetic information in an organism.

Single-nucleotide polymorphisms

• replacement of a single nucleotide with another

• create genetic diversity/variation within a single species

Chromosome number

Chromosome number is a shared trait among species. Odd # of chromosomes makes them sterile (e.g, a mule (horse and donkey) has an odd # and cannot reproduce).trait

Haploid (chromosomes)

2 copies of each chromosome

Diploid (chromosomes)

1 copy of each chromosome

Human chromosome number

46 (diploid ) 23 (haploid)

Chimpanzee chromosome number

48 (diploid) 24 (haploid)

Chromosome fusion

The end-to-end joining of two non-homologous chromosomes, resulting in a reduction of the total number of chromosomes. A well-known example in human evolution is the fusion of two ancestral ape chromosomes to form human chromosome 2, which explains the difference in chromosome numbers (46 in humans, 48 in chimpanzees) between the two species.

Aneuploidy

A condition where a cell or organism has an abnormal number of chromosomes, many different types of it (Monosomy, Trisomy, etc.)

Monosomy

A type of aneuploidy where an organism's cells are missing one chromosome from a homologous pair. It could result in intellectual disability, growth deficiencies, distinctive facial features (craniofacial abnormalities), and organ malformations such as heart or kidney problems.

Trisomy

The genetic condition where a person has three copies of a particular chromosome instead of the usual two, resulting in a total of 47 chromosomes instead of the normal 46 in humans. Can result in intellectual disability, heart defects, and distinctive facial features.

Trisomy 21 (down syndrome)

You have 3 copies of chromosome 21. It could result in physical characteristics like slanted eyes and a flat nasal bridge, intellectual disabilities, developmental delays, and a higher risk for specific health issues such as congenital heart defects, vision and hearing problems, sleep apnea, and increased susceptibility to infections and certain cancers.

Chromosome

A structure of DNA and proteins found in the nucleus of eukaryotic cells, responsible for carrying genetic information (genes) from one generation to the next.

Homologous chromosomes

Chromosomes with the same gene sequence, loci, and chromosome length.

Autosomes

Autosomes contain genes that do not play a major role in sex determination. Human chromosomes 1-22 are autosomes.

Sex chromosomes (XY)

Sex chromosomes contain genes that play a major role in sex determination. The 23rd chromosome pair. Female is XX, male is XY. Y chromosome is much smaller than X chromosome. NOT homologous because: not the same size, and the do not contain the same genes.

Locus/Loci (plural)

A genes location

Alleles

Different versions and variations of genes.

Taxon/Taxa

A unit at any level of the hierarchy is called a taxon.

Taxonomy

The scientific classification and naming of organisms

Domain

Carl Woese created a 3 domain classification system using rRNA sequences. rRNA is ribosomal, RNA, rRNA, and some proteins make up the structure of ribosomes. The rRNA sequences fall into 3 distinct groups which became the 3 domains: Bacteria, Archaea, and Eukarya.

Archaea and Eukarya have a more recent common ancestor than Archaea and Bacteria, so they are more closely related.

Kingdom

The second broadest level of Linneau’s taxonomic system, Organisms within a kingdom share fundamental characteristics and evolutionary relationships. Kingdoms are: Eubacteria, Archaebacteria, Animalia, Plantae, Fungi, Protista

Phylum

Organisms within a phylum share a similar overall body plan or general morphology. Phyla also reflect evolutionary relationships, grouping species that are thought to have descended from a common ancestor.

Class

Organisms within a class are grouped together because they share common fundamental characteristics. 

Order

Organisms are grouped into an order based on shared, significant physical traits and other characteristics, though a clear set of rules for its definition is not always followed.

Family

Organisms in the same family have more specific common characteristics than those at higher classification levels like order or class. These shared features are often based on anatomical, physiological, and genetic similarities.

Genus

Groups one or more closely related species, determines the first word in the Binomial Nomenclature of a species.

Species

The most basic and exclusive biological classification, grouping organisms that are similar enough to reproduce fertile offspring together and share a common genetic makeup.

Cladogram

A branching diagram that represents hypotheses about the evolutionary relationships between different groups of organisms (taxa), organized into "clades" based on shared, derived characteristics (synapomorphies).

Clade

A group of species with a single common ancestor and a set of common traits or characteristics. Must include all species that are descended from a common ancestor. Cannot include any species that are not descended from that common ancestor.

Root

Common ancestor shared by the whole tree

Node

Common ancestor shared by the 2+ lineages branching at that point (represents a speciation event). The more nodes there are between species, the more distant their relationship.

Terminal Branch

Represents the extant species at the end of each branch.

Derived Characteristic

A trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants. (A derived characteristic is indicated by a ‘tick‘ mark along the branches of a cladogram.)

Outgroup

Most distantly related species in the cladogram (used as a point of comparison)

Figworts

The original figwort family (Scrophulariaceae) was shown through chloroplast gene analysis to be a paraphyletic group that was incorrectly grouped, and was thus reclassified into five separate monophyletic clades and families

Natural Selection

Inherited variations exist in populations and organisms, and successful variations are more likely to survive, reproduce, and pass their variations on to the next generation. Causes evolution because the variations keep getting passed on, changing future generations.

Gene Flow

Occurs when organisms from one population move to a new area: their genes “flow“ into the gene pool of a new population. Also called genetic drift.

Genetic Drift

(bottleneck effect, founder effect)

Mutation

Change in the DNA sequence of an organism.

Molecular data

Information derived from the analysis of biological macromolecules, particularly DNA, RNA, and proteins, to determine the evolutionary relationships among organisms.

Molecular Clock

A method for dating evolutionary events by analyzing the accumulation of mutations in DNA or protein sequences over time, assuming these mutations occur at a relatively constant rate.

Selective Breeding/Artificial Selection

The process where humans deliberately choose individuals with desirable traits in plants or animals to breed, leading to the enhancement of these traits over many generations and causing evolutionary changes.

Comparative Anatomy

The study of the similarities and differences in the anatomical structures of different species

Homologous structures

Structures on organisms that share a common ancestor and also have similar underlying structures. (bat wing/human arm/dog leg)

Pentadactyl Limbs

A vertebrate limb characterized by its basic five-digit (finger or toe) structure, found in many amphibians, reptiles, birds, and mammals.

Analogous Structure

Structures that are similar in function but evolved completely unrelated to separate species. DID NOT share a common ancestor.

Vestigal Structures

An anatomical feature or behavior that has lost its original function through evolution, remaining as a remnant or trace of an ancestor that possessed the structure's original utility.

Embryology

The branch of biology that studies the formation, development, and growth of an embryo from fertilization to birth.

Biogeography

The study of the distribution of species and ecosystems in geographical space and through geological time.

Convergent Evolution

The process where unrelated species independently evolve similar traits, often in response to similar environmental pressures, resulting in analogous structures.

Divergent Evolution

The process where two or more species or populations evolve from a common ancestor, developing distinct traits over time due to different environmental pressures or geographic isolation, which can eventually lead to speciation.

Adaptive Radiation

The rapid diversification of a single ancestral species into multiple descendant species, each adapted to a different ecological niche.

Law of Superposition

A principle used to establish the relative age of fossils. It states that in any undisturbed sequence of sedimentary rock layers, the oldest layer is at the bottom, and the youngest layer is at the top. 

Radiometric dating

A scientific method used to determine the age of organic materials and fossils by measuring the amount of a radioactive isotope present and comparing it to its decay product.

Transitional fossil

A fossil showing intermediate characteristics between two different groups of organisms, providing evidence for evolution by demonstrating gradual changes over time.

Allopatric Speciation

A new species is created but only when there is a physical barrier dividing the two species locations (I.e. a mountain or big lake/river.)

Sympatric Speciation

A new species evolves in the same area as their ancestor and does not need a new location, then the two species share similar geographical locations.

Postzygotic Barrier

A reproductive isolating mechanism that prevents hybrid offspring (produced from the fertilization of two different species) from becoming viable, fertile adults.

Reduced Hybrid Viability

A postzygotic reproductive barrier where offspring resulting from the interbreeding of two different species fail to survive to adulthood or to reproduce successfully, often due to genetic incompatibilities between the parents' genes.

Reduced Hybrid Fertility

A postzygotic isolating mechanism that prevents members of different species from producing fertile offspring.

Gradualism

Evolution happening slowly (gradually), little changes over a long period of time.

Punctuated Equilibrium

Evolution happens quickly, uneven rapid bursts of evolving followed by long periods of evolutionary stability or staticity.

Polyploidy

The heritable condition where an organism possesses more than two complete sets of chromosomes in its somatic cells.

Diploid

A diploid cell or organism contains two complete sets of chromosomes, one inherited from each parent.

Autopolyploidy

A situation where an organism possesses more than two sets of chromosomes, all derived from a single species.

Alloployploidy

The condition where an organism has more than two complete sets of chromosomes, with each set originating from a different parental species.

Knotweeds

An invasive, herbaceous perennial plant (genus Fallopia) with bamboo-like hollow stems and heart-shaped leaves that spreads aggressively through rhizomes and seeds, disrupting native ecosystems by crowding out native species, altering habitat, and causing soil erosion.

Lamarck

Believed that acquired traits would be passed onto generations (if I dyed my hair purple, my kid would dbe born with purple hair)

Darwin

Believed in natural selection, and individuals with more desirable traits would reproduce more causing more children to be born with these traits, passed on over generations.

Variation

is everyone was the same, no one would reproduce “better“ than the others, all kids would be born with the same traits, no evolution.

Competition

Survival of the Fittest, fight for water/shelter/food

Fitness

An individuals ability to survive and reproduce. Higher means more reproduction → more offspring → evolution.

Survival of the Fittest

Darwin’s belief, if you had higher fitness you would reproduce and survive better, your offspring would reproduce and survive better, so on and so forth.

Adaptation

depending on the environment + other factors, species adapt over time by evolving to be more suitable to the environment.

Structural Adaptation

A physical characteristic, or an inherent part of an organism's body, that has evolved over generations to enhance its survival and reproductive success in a particular environment.

Behavioral Adaptation

An action or behavior an organism performs that increases its chances of survival and reproduction in its specific environment.

Physiological Adaptation

A metabolic or functional trait that an organism possesses, often through genetic inheritance, to survive and reproduce in its environment.

Selection Pressure

An external factor in the environment that influences the survival and reproduction of individuals within a population, thereby driving evolutionary change by favoring certain traits over others.

Key concepts of natural selection

• variation is RANDOM

• variation must be inherited

• The environment determines what is successful (selective pressure)

• There must be differential reproductive success

• Over time, the population will become more well-adapted to the environment.

Sexual Selection

A mode of natural selection where one sex chooses mates based on particular traits, leading to an increase in the prevalence of those traits within the population over time.

Types of Natural Selection

• Directional: A type of natural selection where one extreme of a trait's range is favored, leading to a shift in the population's overall phenotype.

• Stabilizing: This process favors the average (intermediate) phenotype within a population.

• Disruptive selection: This type of selection favors two or more extreme phenotypes while selecting against the intermediate phenotype.

Non-Random Mating

Occurs when individuals choose their mates based on specific traits or preferences, rather than by chance, leading to deviations from Hardy-Weinberg equilibrium.

Sexual Dimorphism

The consistent difference in form between males and females of the same species, beyond the sex organs themselves.

Birds of Paradise

A diverse family known for extreme sexual selection, leading to males with elaborate plumage and displays to attract females.

Gene Pool

All of the genes (and alleles) within a population; the newcomer(s) will bring their genes, which can change the genetic frequencies of the population.

Neo-Darwinism

A theory in biology that combines Charles Darwin's theory of evolution by natural selection with Mendelian genetics and modern population genetics to explain how species evolve through changes in allele frequencies due to natural selection acting on random genetic mutations and recombination.

Endler’s Guppies

Endler found how environment affects the coloration on guppies by placing some guppies (group 1) in an environment with dangerous predators and some (group 2) in an area without predators. He found that with predators, the guppies had duller colors to blend into the rocks and sand, but in areas without, the guppies became brighter in order to attract a mate. Then he moved some from group 1 to a new area without predators to see if they would change, and eventually they got bright as well.