IB Biology A3.1 Diversity of Organisms

Summary

This script delves into the diversity of life, discussing the distinctions between prokaryotes and eukaryotes, and the fundamental characteristics of living organisms. It explores the importance of genetic variation for survival and natural selection. The script also covers Carl Linnaeus's binomial nomenclature, the biological species concept, and the challenges in defining species, such as hybrids like mules and ligers. It touches on DNA's role in organism development, chromosome analysis, genetic diversity, and the implications of genome sequencing for understanding evolution, fighting diseases, and advancing personalized medicine. The script concludes with the creation of a dichotomous key and the innovative applications of DNA barcoding in species identification.

Takeaways

• 🌐 The Earth hosts a vast diversity of living organisms, with estimates ranging from 3 to 100 million different species.
• 🔬 Genetic variation within and among species is crucial for the survival of life, particularly through natural selection.
• 📚 In the 17th century, species began to be named systematically, and in the 18th century, Carl Linnaeus established the binomial nomenclature for consistent species naming.
• 🔑 The binomial nomenclature assigns each species a two-part scientific name: the first part is the genus, and the second is the species, both derived from Latin and written in italics.
• 🤔 The biological species concept defines a species as a group of organisms that can interbreed and produce fertile offspring, sharing a common gene pool.
• 🚫 Some organisms, like mules and ligers, do not fit the biological species concept because they are sterile and cannot reproduce fertile offspring.
• 🧬 DNA evidence has become instrumental in distinguishing populations and species, especially when traditional physical characteristics are not definitive.
• 🧬 Humans (Homo sapiens) have 46 chromosomes, which is close to chimpanzees, highlighting our genetic similarity despite differences in chromosome numbers.
• 🌱 Plants often have a higher tolerance for chromosome mutations, resulting in a wider variety of chromosome numbers compared to animals.
• 🧬 Genetic diversity arises from processes like crossing over during meiosis, which shuffles genes and contributes to the variation within a species.
• 🌐 Genome sequencing has revolutionized species comparison and classification, with the cost dropping dramatically from $100 million to about $1,000, enabling broader applications in science.

Q & A

What is the estimated range of different species living on Earth according to the National Wildlife Federation?

The National Wildlife Federation estimates that there are three to 100 million different species living on Earth.

What is the importance of genetic variation within and among species?

Genetic variation is essential to the survival of life, particularly through natural selection, as it allows species to adapt to changing environments and maintain their existence.

Who is credited with establishing the binomial nomenclature system for naming species?

Carl Linnaeus is the primary scientist credited with establishing the binomial nomenclature system for naming species.

What are the two parts of a species' scientific name and how are they written?

A species' scientific name consists of two parts: the genus (first word, capitalized) and the species (second word, lowercase). Both words are written in italics when typed or underlined when handwritten.

What is the defining feature of a species according to the biological species concept?

The defining feature of a species is the ability to reproduce and have surviving and fertile offspring, sharing a common gene pool.

Why are mules and ligers not considered their own species despite being hybrid organisms?

Mules and ligers are not considered their own species because they are sterile and unable to reproduce and have their own fertile offspring.

How does the process of natural selection contribute to the diversity of species?

Natural selection contributes to the diversity of species by favoring certain genetic traits that enhance survival and reproduction in specific environments, leading to gradual changes and speciation over time.

What is the significance of the number of chromosomes in a species for its reproduction?

The number of chromosomes in a species is significant for reproduction because it ensures that gametes (sperm and egg cells) have the correct number of chromosomes to form a viable zygote with paired chromosomes.

What is meant by the term 'genome' and how does it relate to species diversity?

The term 'genome' refers to all the DNA, including all the genetic information of an individual. The genome sequence, including the number of base pairs and gene sequences, contributes to the diversity of species by encoding the characteristics that allow for adaptation and survival.

How does the process of crossing over during meiosis contribute to genetic diversity within a species?

Crossing over during meiosis contributes to genetic diversity by exchanging segments of chromosomes between homologous chromosomes, creating new combinations of genes in the offspring.

What is DNA barcoding and how is it used to identify species?

DNA barcoding is a technique used to identify species from small samples of DNA by comparing specific gene regions, such as the cytochrome C oxidase subunit I (Cox1) gene in animals, to a database of known sequences.