Evolution & The Taxonomy of Living Things

What is Evolution?

Any change in the heritable traits within a population across a generation.For example spots on the wings of a butterfly,Fur colour in mice, or

How did living things evolved? Charles Darwin

theorized that all life came from a common ancestor like a single celled organism. As time went on, life forms became more complex and diverse.

Origin of the first cell(s).Scientist believed that a

chemical evolution may have produced the first cell. First, inorganic chemicals reacted to produce small organic molecules, which polymerized to form macromolecules. With the origination of the plasma membrane, the first primitive cell (a Protocell) evolved, and once this could replicate, life began.

The Evolutionary TreeEvolutionary tree is a branching

diagram or tree showing the inferred evolutionary relationships among various biological species.

The branch tips represent existing species. The branches connect the common ancestor, and the nodes depict where one species diverged into two or more species.

Evidence of Evolution Fossils are the remains and traces of

past life or any other direct evidence of past life. Most fossils consist only of hard parts of organisms, such as shells, bones, or teeth, because these are usually preserved after death.

SELECTIVE BREEDING OF DOMESTICATED ANIMALS

These domesticated breeds have been developed from wild species, by selecting individuals with desirable traits, and breeding from them.

HOMOLOGOUS ANATOMICAL STRUCTURES

The fact that anatomical similarities exist among organisms provides further support for evolution.

Agents of evolutionary change

Because evolution is based on changes in living organism that makes them more complex and diverse, scientists have discovered that there are agents or factors that causes these changes. These conditions are:Mutations Genetic DriftGene Flow andNatural selection 

Mutations are random alterations in our genes, the result of genes failing to copy themselves properly or exposure to radiation or other chemicals (called mutagens).

Genetic drift is a mechanism of evolution that occurs by random chance rather than natural selection. In genetic drift, a population experiences a change in the frequency of a given allele, prompted by random luck rather than a need for adaptation

Gene flow is also called migration. This is any movement of genes from one population to another. Gene flow includes lots of different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries.

Natural selection

Charles Darwin developed the theory that evolution occurs as a result of natural selection. It is the process by which some individuals produce more offspring than others. Hence to survive, it must compete for food and a mate. The organisms that survive is consider fit for the environment thus the characteristics that helped this ‘fitness’ will be more common in the next generation than those of its less ‘fit’ relatives.

The Taxonomy of Living Things

The taxonomy of living things basically refers to the classification of all living things.

Why is it necessary to classify living organism? It helps to identify different

organisms and place them in their particular group.

It helps us to study them more easily and systematically.

It highlights the relationship between different organism

The characteristics of all the members of a group can be studied by studying the characteristics of a few members only.

Types of Classification system

There are two (2) types of classification system.

Artificial System –this system of classification is based on comparison of one or a few characteristics of a group. By this classification, different organisms could be grouped together.

The natural system

This system of classification is based on comparison of many characteristics of a group. It takes into account many characters such as external structure, internal structure, growth, development, reproduction.

Hierarchical Classification of Organisms

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

So what are domains?

“Domains” are the cell type that an organism has. There are 3 domains:

BacteriaArchaea Eukaryote

Kingdoms

There are five kingdoms:

Monera Protists Fungi Plants Animals

Group Names

Humans House cat

White oak Housefly

Domain Eukarya Eukarya Eukarya Eukarya

Kingdom Animalia Animalia Plant Animalia

Phylum Chordate Chordate Magnoliophyta

Arthropoda

Class Mammal Mammal Magnoliopsida

Insect

Order Primates Carnivora Fagales 

Diptera

Family Hominidae Felidae Fagaceae Muscidae

Genus Homo Felis Quercus Musca

Species sapiens domestica Alba domestica

GENERAL PLAN OF CLASSIFICATION

All classifications involve systematic grouping of basic units.

• The basic unit of biological classification is species.

• A species refers to a group of organisms that closely resembleeach other and can reproduce among themselves.

• Similar species are grouped into a genus.

• Similar genera (plural of genus) are grouped into a family.

• Similar families are grouped into an order.

• Similar orders are grouped into a class.

• Similar classes are grouped into a phylum

Binomial NomenclatureIn binomial nomenclature, the name of an organism is composed of two words in Latin. The first word is the name of the genus and is called the generic name. The second word refers to the name of the species and is called the specific name. The first letter of the generic name is always written in capital letters whereas the first letter of the specific name is written in small letters. The scientific names are italicized in printing and underlined while writing. Example Homo sapiens Musca domestica