Big Idea 4: Biological Systems Interact, and These Systems and Their Interactions Possess Complex Properties


All biological systems are composed of parts that interact with each other. These interactions result in characteristics not found in the individual parts alone. In other words, “the whole is greater than the sum of its parts.” All biological systems from the molecular level to the ecosystem level exhibit properties of biocomplexity and diversity. Together, these two properties provide robustness to biological systems, enabling greater resiliency and flexibility to tolerate and respond to changes in the environment. Biological systems with greater complexity and diversity often exhibit an increased capacity to respond to changes in the environment.

At the molecular level, the subcomponents of a biological polymer determine the properties of that polymer. At the cellular level, organelles interact with each other as part of a coordinated system that keeps the cell alive, growing and reproducing. The repertory of subcellular organelles and biochemical pathways reflects cell structure and differentiation. Additionally, interactions between external stimuli and gene expression result in specialization and divergence of cells, organs and tissues. Interactions and coordination between organs and organ systems determine essential biological activities for the organism as a whole. External and internal environmental factors can trigger responses in individual organs that, in turn, affect the entire organism. At the population level, as environmental conditions change, community structure changes both physically and biologically. The study of ecosystems seeks to understand the manner in which species are distributed in nature and how they are influenced by their abiotic and biotic interactions, e.g., species interactions. Interactions between living organisms and their
environments result in the movement of matter and energy.

Interactions, including competition and cooperation, play important roles in the activities of biological systems. Interactions between molecules affect their structure and function. Competition between cells may occur under conditions of resource limitation. Cooperation between cells can improve efficiency and convert sharing of resources into a net gain in fitness for the organism. Coordination of organs and organ systems provides an organism with the ability to use matter and energy effectively.

Variations in components within biological systems provide a greater flexibility to respond to changes in its environment. Variation in molecular units provides cells with a wider range of potential functions. A population is often measured in terms of genomic diversity and its ability to respond to change. Species with genetic variation and the resultant phenotypes can respond and adapt to changing environmental conditions.

For Your Information:

Aquatic Biomes

Terrestrial Biomes

The Nitrogen Cycle

Enduring understanding 2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.

Essential knowledge 2.D.1: All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic
and abiotic interactions involving exchange of matter and free energy.




Chapter 52 Presentation-An Introduction to Ecology and the Biosphere


Enduring understanding 2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.
Enduring understanding 4.A: Interactions within biological systems lead to complex properties.
Enduring understanding 2.A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter.


Essential knowledge 2.D.1: All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
Essential knowledge 4.A.5: Communities are composed of populations of organisms that interact in complex ways.
Essential knowledge 2.A.1: All living systems require constant input of free energy.




Chapter 53 Presentation-Population Ecology

Enduring understanding 2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.
Enduring understanding 4.A: Interactions within biological systems lead to complex properties.
Enduring understanding 4.B: Competition and cooperation are important aspects of biological systems.
Enduring understanding 2.E: Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination.
Enduring understanding 4.C: Naturally occurring diversity among and between components within biological systems affects interactions with the environment.


Essential knowledge 4.B.3: Interactions between and within populations influence patterns of species distribution and abundance.
Essential knowledge 2.D.1: All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
Essential knowledge 2.E.3: Timing and coordination of behavior are regulated by various mechanisms and are important in natural selection.
Essential knowledge 4.A.5: Communities are composed of populations of organisms that interact in complex ways.
Essential knowledge 4.A.6: Interactions among living systems and with their environment result in the movement of matter and energy.
Essential knowledge 4.C.4: The diversity of species within an ecosystem may influence the stability of the ecosystem.
Essential knowledge 2.D.1: All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.





Chapter 54 Presentation-Community Ecology

Enduring understanding 2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.
Enduring understanding 4.A: Interactions within biological systems lead to complex properties.
Enduring understanding 2.A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter.


Essential knowledge 2.D.1: All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
Essential knowledge 4.A.6: Interactions among living systems and with their environment result in the movement of matter and energy.
Essential knowledge 2.A.1: All living systems require constant input of free energy.




Chapter 55 Presentation-Ecosystems