Glowing "green scale" Earth sitting in front of flowery background

Living Environment


    Key Idea 1: Living Vs. Nonliving Things

    Key Idea 1 states that, “Living things are both similar to and different from each other and from nonliving things.” 

    Put another way, this Key Idea asks you to show what you know about how living and nonliving things rely on certain processes to stay alive and reproduce. 

    So, what specific concepts fall under this key idea? Here’s a short list of the concepts you need to understand and be able to explain pertaining to Key Idea 1 on the Living Environment Regents Exam: 

    • Diversity of populations within ecosystems and stability of ecosystems, which includes
      • How populations are categorized based on the function they serve in the food web (e.g. producers, consumers, decomposers)
      • How nonliving environments and living populations interact to compose a total ecosystem
      • How different species hold each other in check
      • How disruptions in the numbers and types of species and/or environmental changes can upset ecosystem stability
    • Structures and functions of the human body at different organizational levels (e.g. systems, tissues, cells, organelles), which includes
      • The human digestive, respirative, reproductive, circulatory, and excretory systems, as well as human movement, coordination, and immunity; how these systems interact to perform the life functions. 
      • How disruptions in any human system can cause imbalance in homeostasis
      • The different types of cells in the human body and their various functions
      • The structure of the different types of cells in the human body
      • The functions performed by specific structures within cells, including cytoplasm, mitochondria, ribosomes, cell membrane, vacuole, and nucleus. 
      • The role of receptor molecules in cellular communication
    • How one-celled organisms are able to function, specifically
      • How the structures present in some single-celled organisms cause them to act in a manner similar to the tissues and systems found in multicellular organisms. 


    Key Idea 2: Genetics and DNA

    Key Idea 2 states, “Organisms inherit genetic information in a variety of ways that result in continuity of structure and function between parents and offspring.” 

    This Key Idea is all about how genetics and reproduction work in organisms from all kingdoms. This requires a full understanding of DNA!

    Here are the concepts you’ll need to understand related to Key Idea 2 on the exam: 

    • How the structure and replication of genetic material result in offspring that resemble their parents, including
      • How genes can be modified by interactions with the environment
      • Heredity
      • Where genetic information is located within cells
      • How reproduction works in asexually reproducing organisms
      • The role of sperms and eggs in sexual reproduction
      • The structure and function of DNA in the reproductive process
      • Gene mutations
      • The types of molecules that carry out the work of the cell, particularly protein molecules
    • How the technology of genetic engineering allows humans to alter genetic makeup of organisms, which includes
      • Selective breeding
      • Use of different enzymes to cut, copy, and move DNA segments and insert them into new organisms
      • Altering genes through insertion, deletion, or substitution of DNA
      • New fields of healthcare geared toward fighting diseases that are the result of genetic mutations




    Key Idea 3: Evolution 

    Key Idea 3 states, “Individual organisms and species change over time.” In other words, Key Idea 3 is all about evolution. 

    This idea asks students to be able to explain how evolution works, be able to distinguish between evolutionary change and the changes that occur in the lifetime of an individual organism, and describe the role of natural selection in biological evolution and the diversity of life on Earth today. 

    Here are the main concepts you’ll need to know pertaining to Key Idea 3: 

    • Explain the mechanisms and patterns of evolution, including 
      • The basic theory of biological evolution
      • Genetic mutations, sorting, and recombination 
      • Natural selection
      • Extinction of species


    Key Idea 4: Reproduction, Growth, and Aging 

    Key Idea 4 states, “The continuity of life is sustained through reproduction and development.” This key idea involves knowledge about asexual reproduction and sexual reproduction, growth, development, aging, and reproductive technology. 

    Concepts you need to know for this key idea include

    • How organisms, including humans reproduce their own kind
    • Asexual reproduction
    • Sexual reproduction, including knowledge of
      • Meiosis and fertilization
      • Gametes and zygotes
      • Mitosis
    • The role of gene expression, hormones, and the environment in human reproduction and development
    • The structures and functions of the female reproductive system
    • The structures and functions of the male reproductive system
    • Human embryonic development and possible risks to the embryo due to genetic faults and/or exposure to environmental factors



    Knowing the process of photosynthesis is one of the elements of Key Idea 5. 


    Key Idea 5: Homeostasis 

    Key Idea 5 states, “Organisms maintain a dynamic equilibrium that sustains life.” 

    The central concept to this key idea is homeostasis. Organisms have a diversity of homeostatic feedback mechanisms that maintain dynamic equilibrium. When these mechanisms fail, it can result in disease or even death. You’ll need to understand how homeostasis works in order to successfully communicate your knowledge of this Key Idea. 

    Here are some specific concepts you’ll need to be able to explain: 

    • Explain the basic biochemical processes in living organisms and their importance in maintaining “dynamic equilibrium,” or homeostasis. These processes include: 
      • Photosynthesis, the structure of plant cells, and the structure of one-celled organisms
      • Organic compounds and chemical energy
      • Cellular respiration
      • The storing of energy in ATP molecules
      • The biochemical processes of breakdown and synthesis and the role of enzymes in biochemical processes
      • How the specific shapes of enzymes, hormones, receptor molecules, antibodies, and other molecules influence their interactions with each other
    • Explain disease as a failure of homeostasis
      • How viruses, bacteria, fungi, and other parasites interfere with the normal life functions of plants and animals
      • The immune system and white blood cells
      • Vaccinations
      • Allergic reactions
      • The role of biological research in responding to diseases in plants and animals
    • Relate processes at the system level to the cellular level in order to explain dynamic equilibrium in multi-celled organisms
      • Explain feedback mechanisms that maintain homeostasis


    Key Idea 6: Ecology

    Key Idea 6 states, “Plants and animals depend on each other and their physical environment.” 

    This key idea asks you to be able to articulate how ecological processes work, including competition between members of different species and within species, and to be familiar with the concept of food chains and webs. 

    Specific concepts related to ecology that you need to know include

    • Factors that limit growth of individuals and populations, including
      • How energy flows through ecosystems;
      • How the atoms and molecules on the Earth cycle among the living and nonliving components of the biosphere
      • How the chemical elements that make up the molecules of living things pass through food webs
      • How available energy, water, oxygen, and minerals limit the number of organisms a habitat can support
      • The various types of relationships that organisms can have, e.g. producer/consumer, predator/prey, or parasite/host
    • The importance of preserving diversity of species and habitats
    • How the living and nonliving environments change over time and respond to disturbances, including
      • Ecological succession
      • The role of climate change and natural disasters in altering stable ecosystems


    Key Idea 7: Human Impact on the Environment 

    The seventh and final Key Idea that is included on the Living Environment Regents Exam states, “Human decisions and activities have had a profound impact on the physical and living environment.” 

    This Key Idea is asking you to think about how human activity affects and changes the living environment, causing or perpetuating phenomena like pollution, deforestation, extinction of species, global warming, and alteration of the ozone shield. This key idea is also politically oriented: it asks students to think critically about how they can make a difference environmentally literate citizens in the world.

    You’ll need to know the following concepts:

    • The range of interrelationships of humans with the living and nonliving environment, which includes 
      • How increased human consumption diminishes the earth’s finite resources
      • How natural ecosystems provide basic processes that affect humans, and how human activity changes these processes in negative ways
      • How human destruction of habitats threatens current global stability
    • The impact of technological development and growth in the human population on the living and nonliving environment, which includes
      • How land use and pollution degrades ecosystems and results in a loss of diversity in environments
      • Consequences of adding or removing specific organisms from ecosystems
      • Effects of industrialization, particularly fossil fuels and nuclear fuels, on humans and ecosystems.