Biology

Infraphylum

Inhalation

Inhalation: how air enters the lungs and its roles in respiration

Innate immune system

Innate immune system: first-line defenses, cells, and mechanisms

Inner ear

Inner ear: anatomy, function, evolution and clinical importance

Insectivore

Insectivore: organisms that feed primarily on insects

Instar

Instar — stage in an insect's post-embryonic development

Instinct

Integron

Integron: bacterial gene-capture systems and their role in antibiotic resistance

Integumentary system

Integumentary system: structure, function, and diversity

Intercostal muscle

Intercostal muscles: anatomy, function, and clinical significance

Interferon

Interferon: Immune signaling proteins that protect against viruses and tumors

Intestine

Intestine (digestive tract)

Intrinsic factor

Introduced species

Introduced species: causes, impacts, examples and management

An introduced species is a non-native organism brought to a new area by people. This article explains pathways, ecological and economic impacts, notable examples, and approaches to

Intron

Invasive species

Invasive species: causes, impacts and management

Ion channel

Iris (eye)

Iris (eye) — structure, function, color, and clinical relevance

Irregular bone

Irregular bones (anatomy)

Irritation

Island dwarfism

Island dwarfism (insular dwarfism)

Island dwarfism is the evolutionary reduction in body size seen when large animals become isolated in small, resource-limited environments such as islands, caves, or isolated valle

Islets of Langerhans

Isoform

Isospora belli

Isospora belli (Cystoisospora belli): biology, disease, and management

Jacobson's organ

Jaw

Jaw: structure, diversity, development and function

Jehol Biota

Jehol Biota: Early Cretaceous Lacustrine Ecosystem of Northeastern China

Jejunum

Jelly fungus

Jeotgalicoccus aerolatus

Jeotgalicoccus aerolatus: an environmental Gram-positive bacterium

Jeotgalicoccus coquinae

Jeotgalicoccus pinnipedialis

Jeotgalicoccus pinnipedialis: a marine-associated coccoid bacterium

Joint

Joint (anatomy and classification)

An anatomical joint is the contact point between bones that permits movement and provides support. This article explains joint structure, types (structural and functional), common

Jumping

Karyotype

Kelp forest

Keratin

Keratin: structure, functions, and biological roles

Kidney

Killing

Killing: meanings, types, history, and legal and ethical distinctions

Kin selection

Kinetoplastid

Kingdom (biology)

Kinorhyncha

Kinorhyncha: microscopic marine sediment invertebrates (mud dragons)

Klebsiella

Klebsiella pneumoniae

Knee

Knee (joint) — anatomy, function, common problems and care

Knockout mouse

Knockout mouse: engineered loss-of-function models in biomedical research

Kollikodon

Kollikodon ritchiei — opalised monotreme known from teeth