Living World

Characteristics exhibited by living organisms:

Growth, reproduction, metabolism, cellular organization, consciousness (ability to sense environment), self-replicating, self-regulation and evolution.

• Increase in mass and no of individuals are twin characteristics of growth

GROWTH:

• Occurs by cell division in both multicellular and unicellular organisms
  • Animals: Cell division occurs up to a certain age, after that it occurs to repair damaged tissues
  • Plants: Cell division occurs throughout their life span.
• Can't be a defining factor as ^^non-living things^^ like mountains, boulders and sand mounds ^^also grow due to accumulation^^.

REPRODUCTION:

• Occurs in sexual or asexual methods such as Fungi - spore production; Hydra, Yeast - Budding ; Planaria - True regeneration; Filamentous algae / Protonema of moss - fragmentation

• Not a defining characteristic of growth because ^^some living organisms don't reproduce^^ such as Mule , Sterile worker bees , infertile human couple

• ^^Metabolism, cellular organisation and consciousness^^ are defining properties.

• The sum total of all the chemical reactions occurring in our body is metabolism

• All organisms are ‘aware’ of their surroundings.  Eg : Photoperiod affects seasonal breeders, both plants and animals

• ^^Human beings^^ are the only organisms who are aware of themself, i.e., has ^^self-consciousness^^

DIVERSITY IN THE LIVING WORLD

Biodiversity: Term used to refer to the %%number of varieties of plant and animals on earth%%. The number of species that are known and described range from 1.7 to 1.8 million.

Nomenclature: %%Standardized naming%% of living organism such that a particular organism is known by the name all over the world.

Identification: Correct description of the organisms to facilitate naming

Need for classification: To %%organize%% the vast number of plants and animals into categories that could be named, remembered, studied and understood.

%%ICBN%%: International Code of Botanical Nomenclature (for giving scientific name to plants.)

%%ICZN%%: International Code of Zoological Nomenclature (for giving scientific name to  animals.)

Taxonomy: Study of principles and procedures of classification

BINOMIAL NOMENCLATURE

Given by Carolus Linnaeus.

Each scientific name has two components - %%Generic name + Specific epithet.%%

RULES:

1. Latinized names are used, written in italics.
2. First word represents the genus, second word is species name.
3. Printed in italics; if handwritten then underline separately.
4. First word starts with capital letter while species name written in small letter

Systematics:

It deals with classification of organisms based on their diversities and relationships among them.

Term was proposed by Carolus Linnaeus who wrote ‘Systema Naturae’. It also takes into account about %%evolutionary relationships between organisms%%.

TAXONOMIC CATEGORIES

Arrangement of various steps (categories or taxa )

}}Species → Genus → Family → Order → Class → Phylum (for animals)→ Kingdom}}

(OR)

}}Species → Genus → Family → Order → Class →Division (for plants) → Kingdom}}

SPECIES

• A group of closely related organisms , which can ^^interbreed^^ and can produce fertile offspring's
• Basic unit of classification
• Introduced by Ernst Mayer
• Scientific name for human beings is Homo Sapiens

GENUS

• A group of ^^closely related species^^ which have more characters in common in comparison to species of other genera.
• Potato and Brinjal are two different species but belong to the same genus solanum.
• Lion , Leopard and Tiger are different species belonging to the genus panthera. (Big cats)
• Felis (small cats)

FAMILY

• A group of ^^related genera^^ with ^^fewer similarities^^
• Families are characterized based on both vegetative and reproductive features of plant species.
• Family name of %%animals%% generally end with - %%' idea'%% suffix.
• Family name of %%plants%% generally end with – %%'acea'%% suffix.

Ex:

Family %%Solanaceae%% includes the genus - Solanum, Petunia and Datura.

Family %%Felidae%% includes the genus- Panthera and Felis

Family %%Canidae%% includes the genus- Canis (dogs)

ORDER

• Order is the ^^assemblage of families^^. Which exhibit a few similar characters.
• Eg: Plant families like Convolvulaceae and Solanaceae are included in the %%order Polymoniales.%%

CLASS

• It includes ^^related orders.^^

Eg: Monkey, Gorilla and Gibbon belongs to Order Primata.

Animals of Felidae and Canidae belong to Order Carnivora.

Both Primata and Carnivora are placed %%Class Mammalia.%%

PHYLUM

• Includes ^^related classes^^ in case of animals.

Phylum- %%Chordata%% includes classes – Pisces, Aves, Reptilia and Mammalia.

Based on features like presence of notochord and dorsal hollow neural system.

KINGDOM:

All the plants and animals are included under %%Kingdom Plantae%% and %%Kingdom Animalia%%.

EXAMPLES