The Living World
Unit 1 — Diversity in the Living World
Diversity in the Living World
The Convention on Biological Diversity defines biodiversity as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.”
Taxonomic Categories
A taxonomic category is a rank or level in the taxonomic hierarchy used to classify organisms. There are seven obligate categories and some intermediate categories.
| Category | Definition |
|---|---|
| Species | A species is a natural population, or group of populations, whose individuals resemble one another in essential morphological and reproductive characters and can interbreed to produce offspring. For example, the mango tree (Mangifera indica) belongs to the genus Mangifera. |
| Family | A family is a taxonomic category that contains one or more related genera. The families Felidae and Canidae belong to the same order, Carnivora. |
| Order | An order is a taxonomic category that groups related families. For example, Felidae and Canidae belong to the order Carnivora. |
| Class | A class is made up of one or more related orders. Dicotyledonae is a class of flowering plants. |
| Phylum | The term phylum is used for animals while division is used for plants. Each comprises one or more classes. In animals, the phylum Chordata includes mammals, birds, reptiles and amphibians. |
| Kingdom | Kingdom is the highest taxonomic category. All plants belong to the kingdom Plantae, while all animals belong to the kingdom Animalia. |
Three Domains
Carl Woese, 1990
Archaea
Extremophiles: methanogens, halophiles and thermoacidophiles.
Bacteria
Cyanobacteria and other eubacteria, including beneficial bacteria and pathogens.
Eukarya
Eukaryotes: protists, fungi, plants and animals.
Organisms and Their Taxonomic Categories
| Common Name | Biological Name | Genus | Family | Order | Class | Phylum / Division |
|---|---|---|---|---|---|---|
| Man | Homo sapiens | Homo | Hominidae | Primata | Mammalia | Chordata |
| Housefly | Musca domestica | Musca | Muscidae | Diptera | Insecta | Arthropoda |
| Mango | Mangifera indica | Mangifera | Anacardiaceae | Sapindales | Dicotyledonae | Angiospermae |
| Wheat | Triticum aestivum | Triticum | Poaceae | Poales | Monocotyledonae | Angiospermae |
Differences Between Catabolism and Anabolism
| Catabolism | Anabolism |
|---|---|
| Catabolism breaks down large, complex molecules into smaller molecules that are easier to absorb. | Anabolism builds molecules needed for the body's functions. |
| The process of catabolism releases energy. | Anabolic processes require energy. |
| Hormones involved in these processes include adrenaline, cytokines, glucagon and cortisol. | Hormones involved in these processes include estrogen, insulin, testosterone and growth hormone. |
| Examples of catabolic processes include proteins breaking down into amino acids, glycogen breaking down into glucose and triglycerides breaking down into fatty acids. | Examples include the formation of polypeptides from amino acids, glycogen from glucose and triglycerides from fatty acids. |
| The potential energy is converted into kinetic energy. | The kinetic energy is converted into potential energy. |
Differences Between Aerobic and Anaerobic Respiration
| Aerobic Respiration | Anaerobic Respiration | |
|---|---|---|
| Definition | Uses oxygen to break down glucose in the body. | Uses a respiratory electron transport chain but does not use oxygen as the electron acceptor. |
| Cells that use it | Aerobic respiration occurs in most cells. | Anaerobic respiration occurs in bacteria, yeasts, some prokaryotes, erythrocytes (red blood cells) and muscle cells. |
Taxonomical Aids
Taxonomical Aids
- Herbarium
- Botanical Garden
- Museum
- Zoological Park
- Keys
- Flora
- Manual
- Monograph
Critical Points
Taxonomic Key
A taxonomic key is a set of contrasting characters arranged in sequence so that organisms can be identified through selection and elimination.
- Bracketed key
- Indented or yoked key
Founder of Taxonomy
Aristotle
Dendrogram
When a cladogram is based on numerical taxonomy, it is called a dendrogram.
The sequence of taxa shown in the Linnaean hierarchy is:
- Class
- Order
- Family
- Genus
- Species
Monotypic Genus
A monotypic genus contains only one species, for example, Homo.
Polytypic Genus
A polytypic genus contains more than one species, for example, Panthera and Solanum.