• This definition focuses entirely on observable morphology (external appearance and internal structure).

bi: two

nomial: name

nomenclature: naming system

-> Developed by Linnaeus in 1700s and is updated periodically at a series of international congresses.

-> it is the international standard used by scientists for naming species.

Gene: a segment of DNA that codes for a particular protein

Unity → Species have the same genes in the same positions on their chromosomes

Diversity → The genes themselves can have different base sequences (alleles)

• Provides a straightforward, visual method of classification without requiring complex tools.

• Useful when only fossils or external features are available.

• Enables field-based identification of organisms, which remains valuable in ecology and biodiversity studies.

Limitations

• Morphologically similar organisms may not be closely related.

• Morphologically different individuals may still belong to the same species.

• Fails to account for cryptic species, which are genetically distinct but appear similar.

Karyotyping: process of pairing & ordering the complete set of chromosomes within a cell, to provide a snapshot of an organism’s genetic profile. The chromosomes can then be photographed to generate a visual representation called a karyogram

Karyogram: photographs/diagrams in which the chromosomes of an organism are shown in in homologous pairs of decreasing length

to prepare:

• Cells are cultured+allowed to divide

• Chemicals used to arrest cells in metaphase (organized and condensed)

• Stained

• observed/photographed using a microscope

• organized in decreasing size

This means that variation is essential for the continuity of life in order to survive and change on earth, creating biodiversity.

• The human genome is approximately 3.2 billion base pairs (or 3,200 Mbp) in length.

• Genome size can vary dramatically between species, from less than 1 Mbp in some bacteria to over 100,000 Mbp in certain plants.

• Base pairs (bp): The smallest unit, representing a single pair of nucleotides.

• Kilobases (kb): 1,000 base pairs.

• Megabases (Mb or Mbp): 1,000,000 base pairs.

• Gigabases (Gb): 1,000,000,000 base pairs.

✓Allows for the identification and comparison of organisms based on recognized characteristics

✓Allows all organisms to be named according to a globally recognized scheme à international collaboration/cooperation

✓Can show how closely related organisms are, allowing for the prediction of evolutionary links

✓Facilitates collection, sorting and grouping information about organisms

Single-nucleotide polymorphism

(SNP)

SNP: a position where there are differences in base sequences

Humans 5000 SNPs (out of 3 billion)

• to identify chromosome abnormality

  -> leading to abnormal conditions/syndromes

• determining species types, because chromosome is a characteristic feature

• determining the sex of the organism (XY or XX)

Neonatal Screening: The expansion of genome screening programs for neonates could facilitate the detection of genetic disorders, which supporting the early implementation of targeted interventions and significantly improving patient health.

Oncological Surveillance: Advancements in genomic monitoring, such as tumor, more sensitive and earlier detection of neoplastic disease (abnormal growth of cells --> tumour & cancer), informed monitoring of disease progression or recurrence, and personalization of cancer treatment.

Genome Editing and Therapeutics: Whole genome sequencing allows precise gene-editing initiatives (e.g., CRISPR technologies), enhancing the identification of optimal therapeutic targets and off-target effect mitigation in somatic and germline interventions

It means that humans - chimps share a recent ancestor

it is hypothesized that chromosome 2 in humans arose from the fusion of chromosomes 12 and 13 in the primate ancestor

- There is an online database containing information on DNA sequence

The function of the database:

• Select a specific gene to compare

• Select species to compare

• Choose whether to compare amino acid sequences or DNA base sequences

- Comparison of eukaryotic species sequence data shows that the closely related organisms have more similar genes

A group of organisms that are reproductively isolated from each other, they cannot interbreed and produce fertile offspring.

There are some difficulties in defining the species concept, such as:

1. Asexual reproduction

   • The Biological Species Concept (based on interbreeding and producing fertile offspring) doesn’t work for organisms that reproduce asexually, like bacteria.

2. Fossil species

   • We can’t test whether extinct organisms interbred, so we rely only on morphology, which can be misleading.

3. Ring species

   • In some cases, populations of the same species are distributed in a ring shape around a geographic barrier. Neighboring populations can interbreed, but populations at the ends of the ring cannot, making it hard to draw a clear species boundary.

4. Hybridization

   • Different species sometimes interbreed (e.g., lions × tigers, or plants like wheat species), producing hybrids. This blurs the boundaries between species.

5. Cryptic species

   • Some species look almost identical morphologically but are genetically distinct and do not interbreed. Relying on appearance alone can fail here.

6. Variation within a species

   • Members of the same species can look very different (due to age, sex, environment, or genetic diversity), making classification difficult.

7. Different definitions

   • There are multiple competing species concepts (Biological, Morphological, Phylogenetic, Ecological, etc.), and each works better in some cases than others.

When a single population begins to split, the two groups may show some genetic and morphological differences, but they can still interbreed.

At this stage, it’s unclear whether they are just diverging populations or already separate species.

1. Non-coding DNA: Many genomes contain large amounts of non-coding DNA, which does not directly code for proteins.

   • Repetitive sequences, transposons, and introns all contribute to genome size.

2. Polyploidy: The presence of multiple sets of chromosomes, common in plants, increases genome size.

3. Gene duplication: The duplication of genes or entire genomic regions can lead to larger genomes.

• Animal Genome Size Database: A comprehensive resource for animal genome sizes.

• Plant DNA C-values Database: Contains genome size data for over 10,000 plant species.

• NCBI Genome Database: Provides genome size information alongside other genomic data.

In genetics, the C-value is the amount of DNA in the haploid genome of an organism. It represents the amount of DNA contained within a single set of chromosomes or a single gamete.

The C-value Paradox

The C-value paradox highlights the discrepancy between the amount of DNA (C-value) and the complexity of the organism. 

The paradox emphasizes that functional genes and their regulation, not total genome size, determine organism complexity