A 3.1 SL Diversity of organism Flashcards
Who observed variation between species? And why is it important?
Charles Darwin observed that typical populations vary in many respects, and that this variation is an important factor for evolution. If all individuals in a population were identical, there would be no way of some individuals being favoured more than others.
What was originally the term species used for? And what did Carl Linneaeus discorver?
Originally biologists used the term “species” for a group of organisms with shared traits. Carl Linneaeus, a biologist working on classifying organism, described the outer form and inner structure of typical members of a species according to its morphology.
How did Carl Linneaeus classify plants?
Carl Linnaeus classified plants based on the number, arrangement and fusion of sexual parts. Or, grouping organisms according to the presence of shells would put snails & turtles in the same group….
What is the morphological species concept?
The morphological species concept describes species based on how they look (morphology). This is the traditional way of classification, but it can be very misleading for identifying species. Often two species look similar, but in reality they have evolved differently for a very long time.
Why do biologists group organisms?
Biologists group organisms to represent similarities and proposed relationships. Classification systems change with expanding knowledge about new and well-known organisms. The science of classification is referred to as taxonomy.
What is binomial system for naming organisms?
Categorising organism is easier if a universal and internationally accepted system for naming is used. This two-part name consists of the genus name and the species name.
What is smallest taxonomic group? And how do you incorporate it in the naming system?
How can you recognise subspecies?
three names
What is a species?
A group of individuals of common ancestry that closely resemble each other & that are normally capable of interbreeding to produce fertile offspring.
What is variation?
Variation = Differences in any aspect of an organism.
What is a defining feature of life?
All living organisms show variation. No two individuals are identical in all of their traits. This variation is one of defining features of life.
What has been developed due to variation between organisms?
Bc of large amount of variation between organisms, we have developed systems of classification to group & organise our knowledge about them. These systems structure our understanding & allow for clearer communication between ppl studying organisms around world. ‘Modern’ system for classifying living organisms was published in 1735 by Carl Linnaeus, a Swedish naturalist.
What is a classification of organisms?
A system of organising knowledge on all living things based upon their characteristics & more recently their DNA.
How did Linnaeus classify organisms into species?
Linnaeus classified organisms into species based on shared morphological characteristics. Individuals of same species tend to look more similar to each other than to members of other species. This is original morphological concept of a species.
Define morphological species concept
The morphological species concept relies on morphological data & emphasizes groups of physical trait that are unique to each species.
What is the original morphological concept of a species?
Classification of organisms into species based upon shared morphological (physical) characteristics.
How dos the morphological concept work from lions and tigers?
Take lions (Panthera leo) & tigers (Panthera tigris), these two species of large cats are closely related but separate species, with recognisable, distinct characteristics. Once you recognise what those characteristics are, you wouldn’t confuse a tiger and a lion.
What naming convention did Linnaeus developed for naming species?
Today, this is known as binomial nomenclature. Species are named using both their genus and species names. Genus name comes 1st & 1st letter is capitalised, followed by species name in lowercase. This is put in italics within text or underlined when handwritten. E.g. Homo sapiens, Homo neanderthalensis, Panthera leo & Panthera tigris.
Define binomial nomenclature
Binomial nomenclature: Naming system for living organisms using 2 names for each species; genus followed by species.
Define genus
Genus: Taxonomic group below family & above species. It’s used in binomial nomenclature along with species, as 1st of 2 names.
What do species with the same genus share in common?
Species sharing a genus share common characteristics.
How are species binomial names created?
Names themselves are based on Latin & have varying origins, from descriptions of specific defining features to names of ppl who 1st discovered or described the species. E.g. humpback whale = Megaptera novaeangliae, meaning big-winged New Englander referring to their extremely long pectoral fins & 1 of locations in which they were 1st encountered by whalers. Dall’s porpoise, Phocoenoides dalli, is named after American naturalist William Healey Dall, who collected 1st specimen of species.
Define sexual dysmorphisms
When the male and female of a species look significantly different. Often having completely different features and appearance.
How do we define species that look so similar they can’t be easily distinguished from each other? How do we classify when there is sexual dimorphism within a species and males and females have very different characteristics?
To deal with these issues, among others, the biological species concept was developed.
What is the biological species concept?
This describes an alternate method for defining species with a basis not on morphology but rather on the ability to interbreed & produce fertile offspring. It relies on behavioural info & emphasizes reproductive isolation between groups. A species thus is a group of organisms that can potentially interbreed & produce fertile offspring.
According to this concept, if members of two different species do interbreed, what will occur?
If members of 2 diff species do interbreed, any offspring produced will be infertile & unable to produce their own offspring.
What is an infertile offspring from two different species know as?
These (infertile) offspring between two different species are known as hybrids.
What is the most common example of a hybrid?
One such example = mule, which is produced by breeding a horse with a donkey. Two mules are unable to breed to produce more mules. This can only be done by breeding more horses with donkeys.
Why is the biological species concept not a strict biological rule?
- There have been cases of 2 diff species producing fertile offspring. One such example is a liger, produced when a lion & a tiger interbreed. Ligers are hybrids that challenge the biological species concept as they are fertile and they can interbreed with other lions, tigers or ligers leading to a blurring of species boundaries.
- Biological species concept cannot be applied to organisms that reproduce asexually.
Why does the morphological and biological species concept have challenges and universally applied?
This is bc biological systems are incredibly complex, determination of just how things work is a very challenging task for biologists. As such, there are competing definitions of what a species is, & scientists may use these based on their context of study. In summary, there is no one-size-fits-all definition of a species & it remains fluid and debatable.
How is DNA organised in eukaryotes?
The DNA of eukaryotes is organised into chromosomes within nucleus of cells. Each species has a set number of chromosomes that is common to all members of that species. E.g. humans (Homo sapiens) have 22 pairs of autosomes (numbered 1-22 based on length) & 2 sex chromosomes (either X or Y). Each individual has 46 chromosomes in total in each of their diploid cells.
Which species are most closely related to?
Chimpanzees (Pan troglodytes), our closest living relatives with whom we share over 98% of our DNA, have 23 pairs of autosomes & 2 sex chromosomes. Each individual has 48 chromosomes in total in each of their diploid cells. As diploid cells contain pairs of chromosomes, they will always contain an even number.
What is speciation?
Speciation describes formation of a new species from the splitting of one pre-existing species into two or more new species.
What are the causes of speciation?
- Reproductive barriers could prevent or limit interbreeding between 2 pops. A physical barrier might exist between two pops preventing interbreeding, or there might be a change in behaviour or timing around reproductive cycles.
- Occasionally, a sudden event that changes chromosome number can occur & this sometimes results in creation of a new species. This is often due to an error occurring during cell division where chromosomes don’t separate as they should, producing cells with twice as many chromosomes than they should have.
How long does speciation take to occur?
Speciation events often take a very long time after physical splitting of a population.
How is it possible to visibly compare the chromosomes of two individuals?
Karyotyping, which involves isolating condensed chromosomes taken from actively dividing cells, allows for this comparison.
Define Karyotyping
Determining or analysing karyotype (number, size & shape of chromosomes) of an individual.
How is karyotyping undergone?
The individual chromosomes are stained to highlight banding patterns & images can be arranged to create matching pairs.
Define karyogram
The image created by sorting, matching & aligning chromosomes of an individual allowing for visual interpretation of chromosome characteristics.
How do you analyse a karyogram?
If chromosomes are isolated at correct point in cell division, chromosomes have replicated & can be seen as sister chromatids joined at their centromere, location of which also helps distinguish between them.
How are the chromosomes arranged in a karyogram?
Chromosomes are paired & ordered based on size/length, centromere location & banding patterns. Sex chromosomes in this case are unmatched in length as they are X & Y making this individual a male. X chromosome contains more genes & is therefore longer than Y chromosome that only has a small number of male-specific genes. If this individual was female sex chromosomes would match as they would be XX.
What the similarities between a human and chimpanzee karyogram?
Looking at karyograms for both humans & chimpanzees, it was suggested that at some point chromosomes 12 & 13 of great ape karyotype fused, creating what is now chromosome 2 in human karyotype. On further investigation, there are several pieces of evidence supporting this hypothesis:
- genes of chromosome 2 closely match those of two suspected fusion chromosomes in chimpanzees.
- Telomeric DNA, repetitive sequences found at ends of chromosomes where they help protect the ends of chromosome from damage, were found at suggested fusion region of chromosome 2.
- There is a second centromere region, site where cell’s cytoskeleton attaches to chromosome during cell division, but this one has mutated & doesn’t function.
What shows unity within a species?
A genome is all of the genetic information of an organism. Within most species the genome is very much the same.
What causes diversity within a species?
Usually only single-nucleotide polymorphisms (SNPs) to contribute to variation and diversity, in genome. An SNP 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.
What can cause very large differences in genomes between different species?
There are two main ways in which genomes differ: size & base sequences.
-Size of a genome = actual amount of genetic material, as determined by the number of base pairs. E.g. blue whale (Balaenoptera musculus) has a genome size of 2374.87 million base pairs while humpback whale has a genome size of 2265.79 million base pairs.
- Base sequences of a genome largely determines how DNA is expressed & what genetic characteristics species will have.
How do we compare genome size?
We can compare genome sizes using online databases, which store genetic info for all species whose genomes have been sequenced to date.
What is genome sequencing? And why isn’t it used more?
- Process of determining order of bases in an organism’s genetic code.
- Genome sequencing is a costly & slow process.
What possible ability can be provided from genome sequencing?
The ability to sequence genomes of diff species opens up a whole new world of investigation into genetics & evolutionary relationships among all life on Earth. Provided we can extract enough DNA for analysis, we can compare our genome with that of other great apes & that of any fossilised remains of other human species either already known or newly discovered.
How has genome sequencing improved our classification systems?
Comparison of genomes has also allowed for revision of current classification systems to see whether any reorganisation is required. E.g. red panda (Ailurus fulgens). Initially, it was thought to be closely related to giant panda (Ailuropoda melanoleuca) & to raccoons & other similar mammals. Over time, comparisons were made suggesting it could be included in either of these groups; however, recent genetic analysis has placed red pandas within the superfamily Musteloidea, which includes weasels, raccoons, skunks…
In the future, what abilities could genome sequencing provide us with?
May be able to create personalised medical treatments & interventions based on the sequencing of our own genomes or genome of microorganisms that live symbiotically within us.
Define the ecological species concept
Ecological species concept relies on detailed info about how organisms interact with their biotic (biological) & abiotic (non-living) environment.
Define Evolutionary species concept
Relies on genetic data & emphasizes distinct evolutionary links between groups
Discuss the benefits and disadvantages of using morphology to distinguish separate species.
Benefits:
- easy to distinguish
- simple
- can be useful
- good if no info on reproductive behaviours or genetics
Disadvantages:
- might not actually be genetically the same could both have adapted similarly
- doesn’t take into account mutations
What is a species concept?
A “species concept” is a working definition of a species, helping biologists to group their findings.
What is an example of two species that produce a hybrid that is fertile? But what are the disadvantages?
An example is found in the genus Corvus. The hooded crow (Corvus cornix) & carrion crow (Corvus corone) are closely related species & almost genetically identical. They sometimes mate together in areas of Europe from Scotland to Italy forming fertile hybrids. These hybrids have lower reproductive success than either parental type & hybrid young are less viable (more often die) compared to young produced from unmixed mating.
What is gradual divergence?
Gradual divergence of two populations of a species is this slow process of change, and can eventually form two separate species. This happens when groups of closely related species sometimes increase their geographical range around two sides of a barrier, e.g. a mountain. Pops interbreed with other nearby pops, but not with those on other side of mountain. As time passes each separate group gradually accumulates a collection of mutations in their genes which make them different from other group.
