Classification, Cladistics, and Evolution

evolution

the change in heritable characteristics of populations

Darwinian evolution

due to the tendency to produce more offspring than can be supported by the environment, these individuals aren’t identical and exhibit variations, individuals with variations that help them adapt better to the environment are more likely to survive, reproduce, and pass on the positive variations to their offspring as the individuals will have to compete for resources - natural selection over time, a larger proportion of the population will have these more favorable traits and the species will have adapted

Lamarckian evolution

theory that a change in the environment led to the use of certain organs and disuse of others among organisms, organs that were used more would increase in size over the lifetime of the organisms and organs that were not used would shrink, these changes acquired would be passed on to the offspring

selective breeding

where humans decide the favorable variations, selecting organisms with desirable characteristics and use them as the next generation of parents

homologous structures

indicate divergent evolution, which occurs when organisms arising from the same ancestral species adapt to different environmental conditions according to the pressures of natural selection

analogous structures

body parts that have the same or similar function in different groups of organisms but have different structures

convergent evolution

occurs when distantly related groups of organisms face similar environmental conditions and adapt in similar ways

speciation

the process by which new species arise, it involves the splitting of one ancestral species into two or more descendant species which are genetically different from each other and can no longer interbreed, speciation results in modifying the original gene pool of a species into separate gene pools in a way that interbreeding is prevented

reproductive isolation

refers to barriers that prevent populations of the same species from interbreeding and/or producing fertile offspring, could result from geographical barriers

allopatric speciation

geographic isolation

sympatric speciation

when a new species is formed within the same location due to isolating mechanisms, behavioral and temporal isolation could lead to sympatric speciation

geographic isolation

the separation of species by natural or human-made physical barriers

temporal isolation

a result of differences in the timing of the reproductive cycle, this prevents interbreeding even though the species may share the same geographical location

behavioral isolation

due to environmental factors, organisms of the same species may develop different mating rituals over time, when their potential mates do not recognize these mating rituals, this results in behavioral isolation and the individuals do not interbreed

prezygotic barriers

barriers that prevent the formation of the zygote

postzygotic barriers

barriers that occur after the zygote is formed, could include zygote inviability or sterility

adaptive radiation

describes the rapid evolution of an ancestral species in different lines to utilize the available ecological niches

hybridization

refers to interbreeding between two different species producing offspring known as hybrids

polyploidy

suggested to be the cause of explosions in species diversity, happens when a diploid cell or organism acquires one or more additional sets of chromosomes, called polyploidy, caused due to a non-disjunction of chromosomes during mitosis or meiosis

allopolyploidy

a special case of polyploidy, its a hybrid and has multiple chromosome sets that are derived from the different parental species

binomial nomenclature

naming system for living organisms using two names for each speciees; the genus followed by the species

biological species concept

an alternate method for defining species with a basis not on morphology but rather on the ability to interbreed and produce fertile offspring, developed to deal with issues like sexual dimorphism and when species look so similar they can’t be distinguished

speciation

describes formation of a new species from the splitting of one pre-existing species into two or more new species

karyotyping

involves isolating condensed chromosomes taken from actively dividing cells, allows for the comparison of chromosomes between two individuals

karyogram

the individual chromosomes are stained to highlight banding patterns and the images can be arranged to create the matching pairs of chromosomes

genome

all of the genetic information of an organism

single-nucleotide polymorphisms (SNPs)

occurs when a single nucleotide is replaced with another, much of what makes each person genetically different to every other person is due to these SNPs, contributes to variation and diversity

dichotomous key

a tool used in field work to aid in the identification of organisms, composed of a series of questions or statements based on the physical characteristics of the organisms concerned, each question has only two possible answers - usually stating whether a feature or characteristic is present or not

DNA barcoding

an unknown specimen or environmental sample is collected and DNA is extracted, from this sample certain specific DNA sequences are identified, creating a unique ‘barcode’ for that specimen, the sequences used have been selected because they show much more variation between species than they do within species, the barcode of the specimen can then be compared with a catalogue of barcodes that allows for the identification of species

classification

the sorting and organizing of things or ideas into groups or categories based on a set of criteria

clades

groups of organisms with common ancestry and shared characteristics

cladistics

a way to work out the evolutionary relationships between the species based on shared traits, and genetic evidence

cladistic analysis

a technique based on the idea that shared genetics or traits that have been passed down from a common ancestor are what identify a clade

cladograms

used to compare the traits of various organisms and explore evolutionary links, branching