Planet Earth and Its Environment A 5000-million year Journey

Part of the Patterns in Nature ModuleBiology in Focus, Preliminary CourseGlenda Childrawi and Stephanie HollisPatterns in NatureTopic 9: Cells to SystemsDOT PointIdentify some examples that demonstrate the structural and functional relationship between cells, tissues, organs and organ systems in multicellular organisms. chipstop.savetheforests.org.au

IntroductionOrganisms need to interact with their surroundings, take up substances that they need for their functioning and get rid of wastes which build up as a result of metabolic functions.pbase.com

IntroductionUnicellular organisms are so small that simple diffusion is adequate to supply the organisms requirements and to remove wastes.

Water levels can also be maintained through the passive process of osmosis because the surface area to volume ratio is large enough. davidlnelson.md

IntroductionMulticellular organisms are larger in overall size and so their surface area to volume ratio is smaller. As a result, passive transport would be insufficient to address their needs.

This problem is overcome by the functional organisation of these multicellular organisms.telegraph.co.uk

IntroductionLarge organisms are made up of numerous small cells, so that each cell has its own large surface area to volume ratio. This leads to an increase in the efficiency of diffusion and osmosis in individual cells.publications.nigms.nih.gov

IntroductionMulticellular organism cells are also organised into groups called tissues which are further organised into organs and systems developed to further increase efficiency.anselm.edu

Structure and FunctionFlattened cells like the tissue lining the air sacs in the lungs, or elongated cells like photosynthetic cells in leaves, give a greater surface area to volume ratio than cube shaped cells.nikonsmallworld.com

Structure and FunctionThe exposed edges of cells may also be extended into folds like the root hairs that absorb water and mineral salts in plants or the cells lining the wall of the small intestine that absorb nutrients. redorbit.com

Cell Differentiation and SpecialisationIn multicellular organisms different cell types (tissues) become structurally suited to carry out different functions. This increases their effectiveness in carrying out their functions.

Some cells are involved in obtaining nutrients, whereas other tissues function in movement, growth and excretion.bio.davidson.edu

Cell Differentiation and SpecialisationYoung cells (called embryonic cells) are similar to each other in structure early in life but once it begins to grow and mature they develop suitable structural changes that allow them to carry out specialised functions.aeuts.com

Cell Differentiation and SpecialisationWhen cells become specialised to perform a particular function, they are said to differentiate. They develop suitable structural features which allow them to carry out their functions.

This makes them structurally different from other types of cells and from the embryonic cells from which they arose.nist.gov

Cell Differentiation and SpecialisationOnce they have become specialised to form a particular type of tissue, differentiated cells lose their capacity to develop into other types of cells. Many even lose their ability to divide and give rise to the same type of cells.

Undifferentiated cells are able to divide and differentiate into other types of cells. They are known as stem cells. biologyonline.us

Cell Differentiation and SpecialisationStem cells may be embryonic (found in embryos) or adult stem cells (eg: neural stem cells lining the ventricles of the adult brain or blood producing stem cells in bond marrow)

Stem cell research is a current area of contention. How do you feel about this?topnews.ae

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Cell Differentiation and SpecialisationEmbryonic stem cells can give rise to all other cell types and may be useful for the treatment of injuries and diseases.

This involves harvesting cells from living embryosglobalpharmasectornews.com

Cell Differentiation and SpecialisationThe use of adult stem cells is non-destructive but adult stem cells are only able to give rise to their own particular type of tissue (eg: neural cells give rise to cells of the nervous system)

Current researchers are trying to induce adult stem cells to transdifferentiate into cell types that they do not normally produce.odec.ca

Functional OrganisationJust as similar specialised cells that perform common functions and are arranged together to form tissues, groups of tissues collectively form organs. An organ is an arrangement of different types of tissues, grouped together for some special purpose.

For example, the leaf is an organ for making food. The heart is an organ for pumping blood.mwsu-bio101.ning.com

Functional OrganisationA system is a collection of organs that will all work together to achieve an overall body function. A multicellular organism is composed of many systems which function together cooperatively to ensure its survival.

What do you think would happen if one of these systems malfunctioned?infovisual.info

Activity-Hand out copies of Functional Organisation chart (pg 128-129 Prelim Bio in Focus text)

Students to complete:-Dot Point Question 3.1.1: Complete the following table to distinguish between cells, tissues, organs and organ systems in multicellular organisms.