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  Organizations     Dictionary     Red List of Threatened Species     Photoalbum  
 Dictionary :: biologist 
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Label

Any distinguishing feature of a substance or organism that can allow the monitoring of it, such as the half life  of a carbon isotope.

Lactase

The enzyme responsible for catalysing the split of lactose into galactose  or glucose that is secreted in the intestine to breakdown foodstuff.

Lactation

The production of milk from the mammary glands in mammals, that is induced by the hormone luteotropic hormones secreted by the pituitary gland.

Lactic Acid

An organic compound deriving from pyruvic acid in anaerobic conditions.

Lactogenesis

The production of milk, occurring in the mammary glands.

Lactogenic Hormone

Hormones  that promote the production of milk, see luteotrophic hormone .

Lactose

A disaccharide sugar which is commonly found in milk. It consists of galactose and glucose, where an enzyme called lactase can break lactose into these two smaller components. Microorganisms convert lactose to pyruvic acid, which results in the souring of the milk for example.

Laevulose

The less common name for fructose.

Lamella

A sheet like membrane found within a chloroplast of an autotrophic cell. They acts as a type of wall at which chloroplasts can be fixed within, achieving the maximum light possible.

Lamellae

Plural of lamella.

Lamprey

Pertaining to species of animals who do not possess a jaw bone.

Lapsus Calami

A typing error usually related to misspellings in taxonomic classification.

Large Intestine

The lower part of the gut that provides a tract passage to the anus for excretory material to be removed Larva (pl. larvae) The pre-adult form of many animals.

Larynx

The upper part of the trachea that is surrounded by cartilage which helps to protect the throat and vocal chords situated there.

Lasso Cell

A type of cell that is capable of secreting adhesive material. These cells are present to gather food particles or to capture and nullify prey by using this adhesive material to stick to them.

Latent

Dormant, but with energy potential.

Latent Infection

A type of infection that lays dormant in a host but can still be passed on to others.

Latent Period

The time frame between the presence of a stimulus designed to initiate a response and the actual time where the response is exhibited.

Lateral

Pertaining to the side of something.

Lateral Meristem

Cells capable of growth in plants found in the lateral areas of a plant.

Law of Mass Action

A law stating that the intensity of a reaction is dependent on the degree of presence of the reactants responsible for the reaction.

Leaf

The photosynthetic region of plants, where different species exhibit different types of leaves to suit their function. This diversity of plant leaves has been brought about by natural selection attempt.

Leaf Abscission

See Abscission.

Leaf Area Duration

The long term relationship of information found from the leaf area index, where the volume of ground covered in relation to upper leaf surface area is measured against time.

Leaf Area Index

A type of information worked out by calculating the volume of the upper surface of leaves in relation to the volume of ground that is directly below the plant.

Leaf Blade

The photosynthetic part of a leaf.

Leaf Scar

A scar left on a plant as a result of leaf abscission (abscission).

Learning

An ability in organisms to use past experiences to make informed decisions for a particular situation.

Learning Curve

Learning is a cumulative process, meaning the more you learn about a particular aspect of life, the more you know in principle about it. Trial and error is a method of learning where you get something wrong until you get it right. This is a learning curve. You learn to remember all aspects of "what went wrong" and remember how to do it right, effectively "learning and remembering" it for future similar encounters. See Learning and Memory.

Leaves - Centric

Centric leaves are needle like, almost cylindrical in shape and are commonly found in extreme ecosystems such as desert where the minimal leaf surface means minimal loss of water through transpiration.

Leaves - Dorsiventral

These leaves grow horizontally, so that the majority of photosynthetic cells are facing upwards and receiving light in the day for photosynthesis. The majority of stomata are found on the lower half so that transpiration  does not increase during the day. Dorsiventral leaves can either be 1) simple, consisting of one leave or 2) compound, consisting of many leaves stemming from the same petiole.

Leaves - Isobilateral

These sword like leaves that grow erectly have stomata evenly distributed between its upper and lower sides, and never diversify into compound leaves.

Lens - Eye

Part of the eye that is responsible for distinguishing the spacial distance between the organism and objects in its environment.

Lens - Optical

A type of glass used to refract rays of light in a given direction, as used in microscopes.

Lentic

Still water.

Lenticel

A small pore found near stomata in plants that allows gaseous exchange to occur between the internal and external environments of the plant.

Lethal

Of deadly proportions.

Lethal Allele

A type of genetic mutation that proves to be deadly.

Lethal Gene

A gene's whose effect on the phenotype is profoundly negative, and causes the organism to exhibit many disadvantageous characteristics, which can eventually lead to death.

Lethal Mutation

A type of genetic mutation that proves to be deadly.

Leucine

An amino acid commonly found in proteins.

Leucocyte

Another name for white blood cells or leukocytes, a type of cell that is used in an immune response. They can be differentiated into two groups, granulocytes and agranulocytes, where the former is found more frequently.

Leucocytosis

An immune response, leucocytosis is the presence of a higher than usual amount of leucocytes usually as a result of infection.

Leukaemia

Cancer of leucocytes, resulting in dangerous growth of ineffective and immature white blood cells en masse, leaving the weakened immune system susceptible to infection.

Leukocyte

See leucocyte.

Life Cycle

The period of growth, development, aging and death of an organism.

Ligament

A type of connective tissue interconnecting bones and helping to make the overall structure of the skeleton.

Ligase

An enzyme which is capable of binding two smaller components into one single structure.

Ligation

The joining together of nucleic acids using DNA ligase.

Light

The part of the electromagnetic spectrum  visible to the eye. This varies between blue at 400 nanometres and red at 770 nanometres.

Light Dependant Reaction

The reaction where light required for the photolysis of water in photosynthesis.

Light Independent Reaction

See Dark Reactions.

Light Reactions

Reactions that are dependant on light being available for the reaction to occur, as in the instance of photosynthesis.

Light Year

The distance light can travel in a year through a vacuum, at 186 000 miles per second, it travels 5.9 x 10 to the power of 12 miles Light.

Lignification

The depositing of lignin in cell walls by plants that creates wood.

Lignin

A compound found in cell walls, and this non living component provides a structural function in xylem and bark in plants.

Limb - Animal

A projection from the torso such as a leg or wing.

Limb - Plant

The branch of a tree.

Limiting Factor - Population

Any factor (biotic or abiotic) that inhibits the growth of a species population.

Limiting Factor - Reaction

A factor that limits or completely inhibits the rate of a particular reaction.

Typically, temperature is a major limiting factor in any event, primarily due to the fact the temperature affects the effectiveness of enzymes, which are themselves one of the prime catalysts in executing an efficient and effective reaction.

Limnology

The study of freshwater ecosystems.

Linneaus, Carl

The father of modern taxonomy and modern methods of classification. He was the first to implement binomal nomenclature as a way of differentiating species, and was responsible for the further developments of classifying organisms in a more relevant and fa.

Linoleic Acid

A type of fatty acid that is not naturally produced but required as part of a balanced diet in animals.

Lipase

An enzime capable of breaking down fats into fatty acids and glycerols.

Lipid

(Otherwise known as fat), a fat molecule of which can be divided into five types.

Liposome

An artificially constructed vesicle of a phospholipid

Liquid Feeder

An organism that is dependant of a liquid food diet.

Live Vaccine

A weakened or killed vaccine containing a virus that will be injected into the host. This triggers an active immune response  for a particular antibody which will be memorised by T-Cells for future reference.

Liver

One of the most important organisms of the mammalian body, it is chiefly responsible for the control of glucose concentration in the bloodstream.

Locomotion

Movement.

Locus

The position of a gene on a chromosome.

Long Day Plant

A plant that requires a minimum set amount of hours of sunlight to flower.

Loops of Henle

U shaped structures found in the Bowman's capsule of a kidney nephron that provide a surface area for the re-absorption of water and other materials.

Lotic

Pertaining to running water, an example being a lotic (running water) ecosystem.

Luciferase

An oxidising enzyme acting on luciferin, a substance that gives certain organisms an ability to emit light.

Luciferin

The substance that luciferase acts upon in bioluminescence.

Luminosity

The degree of light emitted by an object or the intensity of it.

Lung

The organ of the body responsible for gaseous exchange between our bodies and the external environment, where oxygen can be absorbed and CO2 exhaled. The lung consists of millions of sac like structures called alveoli that are the site of gas exchange.

Luteinizing Hormone (LH)

A type of hormone produced by the anterior pituitary gland of the endocrine system. In females, this pro.

Luteotrophic Hormone (LTH)

A hormone released by the anterior of the pituitary gland that stimulates production of LH and maternal behaviour.

Lymph Heart

A type of vessel that is responsible for pumping lymph around the body. It is present in animals barring birds and mammals.

Lymph Node

A type of tissue responsible for producing antibodies to fight antigens that is present in birds and mammals.

Lymphatic Node

See lymph node.

Lymphatic Vessel

Vessels that carry lymph material.

Lymphocyte

A type of leucocyte of the agranulocyte group that either differentiate into B Cell or T Cell.

Lys

A shorthand version denoting lysine.

Lysergic Acid Diethylamide (LSD)

A drug will hallucinogenic properties.

Lysis

The rupturing of a cell wall  releasing the contents within the cell.

Lysosome

Lysosomes are organelles capable of phagocytosis as they possess powerful digestive enzymes such as lysozyme.

Lysozyme

An enzyme capable of breaking down cell walls that is used in the immune system to eliminate foreign microbes with its powerful digestive properties.

Lytic Cycle

The life cycle of a bacteriophage.

 

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