STRONA G£”WNA » Lecture - 3 (1DDS program)

Wydzia≥ Lekarski
MD (6-year)
DDS (5-year)
Pharmacy (6-year M.Sc.)


Lecture - 3 (1DDS program)

PREZENTATION (pdf - password)

Host-parasite relationship as one of ecological examples

of interaction between different populations

Types of interactions:
I. Antagonistic;
II. Nonantagonistic;
III. Neutral.

Levels of interaction
intraspecific - interactions among organisms of the same species;
interspecific - interactions among organisms of different species (two or more species).


PREDATION   - a biological interaction where a predator species kills and eats other organisms, known as prey (carnivory, omnivory or herbivory).
Co-evolution - is the mutual evolutionary influence between two species. Each party in a co-evolutionary relationship exerts selective pressures on the other, thereby affecting each others' evolution.
Co-evolution of predator and prey – feeding adaptations in predator and defence adaptation in prey.
The "Red Queen" hypothesis is an evolutionary hypothesis to explain in ecology the constant evolutionary arms race between competing species.
This principle was proposed by the evolutionary biologist L. van Valen (1973), and is based on the Red Queen's race in Lewis Carroll's Through the Looking Glass. The Red Queen said, "It takes all the running you can do, to keep in the same place". The most obvious example of The "Red Queen" hypothesis are the "arms races" between predators and prey.

predator adaptations;

prey adaptations - defensive mechanisms;

Batesian mimicry;

Mullerian mimicry;


advertising and warning colouration;

predator – prey dynamics; the Lotka-Volterra equations.

COMPETITION - an interaction among individuals utilizing limited resources, resulting in reduced fitness in the competing individuals.
Modes of Competition:

Multi-dimensional concept of ecological niche.

Fundamental niche vs. realized niche.

Law of competitive exclusion (Gause’s principle).

Resource partitioning.

AMENSALISM - a biological interaction between two species in which one restricts the success of the other without being affected positively or negatively by the presence of the other. Usually this occurs when one organism exudes a chemical compound as part of its normal metabolism that is detrimental to another organism.

ALLELOPATHY - the production of specific biomolecules by one plant that can harm or give benefit to another plant.
It is most commonly used as an interaction in which one plant causes suffering to another plant.

PARASITISM is an extremely successful mode of life. Depending on the definition used, as many as half of all animals have at least one parasitic phase in their life cycles, and it is also frequent in plants and fungi. Moreover, almost all free-living animals are host to one or more parasite taxa.

SYMBIOSIS is a close ecological relationship between the individuals of two (or more) different species. Sometimes a symbiotic relationship benefits both species, sometimes one species benefits at the other's expense, and in other cases neither species benefits.
Symbiotic relationships may include:
- obligate relationship in which both interacting species benefit;
Commensalism - the commensal species benefits; host species is not affected;
Protocooperation - two species interact with each other beneficially, but they have no need to interact with each other. It is not at all necessary for protocooperation to occur.

NEUTRALISM - describes the relationship between two species which do interact but do not affect each other. It is to describe interactions where the fitness of one species has absolutely no effect whatsoever on that of other. True neutralism is extremely unlikely and impossible to prove. When dealing with the complex networks of interactions presented by ecosystems, one cannot assert positively that there is absolutely no competition between or benefit to either species. Since true neutralism is rare or nonexistent, its usage is often extended to situations where interactions are merely insignificant or negligible.

Additional definitions

Ecological niche - the portion of the environment which a species occupies, defined in terms of the conditions under which an organism can survive, and may be affected by the presence of other competing organisms.

Adaptation. The change in the response of a system over time; functional or structural changes that allow an organism to respond to changes in the environment.

 Author: Piotr Nowosad date: 2020-03-11  print    back  
All rights reserved Department of Biology and Medical Parasitology ® 2020