Introduction to Biology

• Biology studies living organisms, including their origins, anatomy, morphology, physiology, behavior, and distribution.
• The word "biology" comes from the Greek words "bios" (life) and "logos" (study).

Branches of Biology

• Anatomy studies the structures of organisms.
• Biochemistry studies the chemical reactions essential for life, often at the cellular level.
• Bioinformatics uses information technology for the study, collection, and storage of genomic and other biological data.
• Biotechnology involves manipulating living matter, including genetic modification and synthetic biology.
• Botany is the study of plants.
• Cell biology studies the cell as a complete unit, including molecular and chemical interactions within.
• Ecology studies the interactions of living organisms with each other and their non-living environment.
• Genetics studies genes and heredity.
• Immunology studies the immune system.
• Microbiology studies microscopic organisms (microorganisms) and their interactions with other living things.
• Molecular biology studies biology and biological functions at the molecular level, overlapping with biochemistry.
• Pathobiology or pathology studies diseases, their causes, processes, nature, and development.
• Pharmacology studies the interactions between drugs and organisms.
• Physiology studies the functions and mechanisms occurring in living organisms.
• Zoology studies animals, including their classification, physiology, development, and behavior.

Living Things

• Living things are organisms possessing the characteristics of life, including plants, animals, and microorganisms.

General Classification

• Early classification divided living things into plants and animals.
• Plants and animals are both eukaryotic, but differ in characteristics like mode of nutrition and cellular features.
• Animals are typically motile and heterotrophic.
• Plants are typically non-motile, photosynthetic, and possess a cell wall.
• Bacteria and archaea are prokaryotes, setting them apart from plants and animals.
• Bacteria and archaea are single-celled and possess cell walls made of different materials, lacking a nucleus.
• The seven levels of classification are: kingdom, phylum, classes, order, families, genus, and species.

Kingdoms

• Kingdoms represent the most fundamental classification level.
• The five kingdoms are: Animalia, Plantae, Monera, Protista, and Fungi.
• Placement into a kingdom depends on food acquisition, cell type, and cell number.

Phylum

• Phylum follows kingdom in the classification hierarchy.
• It groups organisms based on physical resemblances, suggesting common ancestry within a kingdom.

Classes

• Classes further subdivide organisms within a phylum.
• Organisms in a class share more characteristics than those in a phylum.
• Humans are in the mammal class due to the characteristic of drinking milk as babies.

Order

• Orders break down each class further.
• A taxonomy key, a checklist of characteristics, aids in determining an organism's order.

Families

• Orders are divided into families.
• Organisms within a family share more in common and are considered related.

Genus

• Genus characterizes the generic name for an organism.
• Genus classification is very specific, resulting in fewer organisms per genus.
• The genus is the first part of an organism's two-part name in taxonomy.

Species

• Species is the most specific and lowest level of classification.
• Organisms within a species can breed with each other.
• The species name forms the second part of an organism's two-part name.

Characteristics of the Five Kingdoms

• Animalia: Eukaryotic cells, no cell wall, nuclear membrane present, tissue/organ/organ system level, heterotrophic nutrition.
• Plantae: Eukaryotic cells, non-cellulosic cell wall, nuclear membrane present, tissue or organ level, autotrophic nutrition, includes plants, trees and bushes.
• Monera: Prokaryotic cells, non-cellulosic cell wall present, nuclear membrane absent, unicellular, autotrophic and heterotrophic nutrition, example: bacteria.
• Protista: Eukaryotic cells, cell wall present, nuclear membrane present, unicellular, autotrophic nutrition.
• Fungi: Eukaryotic cells, cell wall present, nuclear membrane present, multicellular, heterotrophic nutrition, example: mushrooms.

Classification Based on Energy Utilization

• Organisms can be classified by energy and carbon source for synthesizing cellular material.

Autotrophs

• Autotrophs produce their own energy-rich organic compounds from inorganic sources.
• They use sunlight (photosynthesis) or inorganic compounds (chemosynthesis) to convert carbon dioxide into organic molecules.
• Plants, algae, and some bacteria are examples.

Heterotrophs

• Heterotrophs obtain energy by consuming other organic matter.
• They rely on autotrophs or other heterotrophs for organic molecules.
• Animals, fungi, and most bacteria are examples.

Photoautotrophs

• Photoautotrophs use sunlight for photosynthesis, converting carbon dioxide into organic molecules.
• Plants, algae, and some bacteria are examples.

Chemoautotrophs

• Chemoautotrophs use energy from chemical reactions, such as oxidizing inorganic compounds, to produce organic molecules.
• Certain bacteria and archaea in extreme environments like hydrothermal vents are examples.

Photoheterotrophs

• Photoheterotrophs get energy from sunlight but rely on organic compounds for carbon.
• They combine photosynthesis with uptake of organic molecules, for example some bacteria and protists.

Chemoheterotrophs

• Chemoheterotrophs obtain both energy and carbon by consuming organic compounds produced by other organisms.
• Animals, fungi, most bacteria, and many protists are examples.