hello and welcome back this video will cover the hierarchy of biological organization we've already talked about the dizzying variety of life on Earth bacteria archaea plants animals fungi and protists so how is it that we can even have a biology class that covers all of life to answer this question let's look a little more closely at what organisms are made of we'll start with our own species homo sapiens we're familiar with what humans look like after all we see each other every day each individual human is what we call an organism or in other words an individual living being but what if we remove the skin and look a little deeper here we are seeing some parts that allow humans to function specifically we are seeing the muscles here which are part of the musculoskeletal system as well as a good chunk of the circulatory system this is a level of organization below that of the organism the organ system note that not all organisms have organ systems single-celled organisms do not of course and some multicellular organisms do not either organ systems are made up of organs which are groups of tissues United to perform a common function here we are seeing on the top a human brain and on the bottom a great animation of a human heart so what happens if we dissect one of these organisms now we'll need to switch to a microscopic view and look at the tissues which are groups of cells that carry out similar or related functions for example the heart can be dissected to see heart tissue cells under the microscope performing their function of contraction which of course when organized in the form of a heart moves the blood in the body plants have tissues as well shown here is a microscopic image of sclerenchyma tissue which helps provide structural support for the plant and this brings us to individual cells which make up tissues the cell is the basic unit of life both in terms of structure and in function in living organisms some organisms consist of just a single cell others like us consist of trillions of cells that need to work together in a coordinated way to sustain life we can zoom in even further to see what cells are made of although cells are fantastically varied they all share some key components all cells have a plasma membrane or in other words a cell membrane that separates the cell from the rest of the universe the plasma membrane also controls the passage of materials into and out of the cell and mediates communication with the surrounding environment all cells also have a fluid filled interior or cytoplasm inside the plasma membrane which includes the cell's organelles and other structures all cells have a genome which is made up of one or more DNA molecules The genome contains the genetic information of the organism and all cells have ribosomes the structures that synthesize proteins which are absolutely essential to all life so cells have organelles inside which are specialized structures that have specific functions these organelles such as the chloroplast the mitochondrion the nucleus and Golgi bodies shown here are made up of molecules molecules are two or more atoms held together by chemical bonds some of these molecules are very large and specific to living organisms we call these biological macromolecules these include nucleic acids such as DNA shown here on the top and RNA as well as proteins shown here on the bottom this is a three-dimensional model of chaperonin shown in two different views and also lipids and carbohydrates we can break these macromolecules down further into monomers most usually monomers are molecules which again are two or more atoms held together by chemical bonds here we're seeing on the top a ball and stick model of water and on the bottom a ball and stick model of the molecule caffeine these are made of atoms which are the fundamental unit of matter in this course we'll largely begin with atoms and work our way up to the higher levels of biological organization by the way there are levels above the organism too organisms of the same species that live in the same area are called a population for example this is a population of wildebeest crossing the mara River in Tanzania populations exist within biological communities which are all of the populations inhabiting a particular area we can go up one more level and talk about ecosystems in biology ecosystems consist of all of the living things in an area plus all of the abiotic or non-living parts of the environment and finally the biosphere includes all of the ecosystems on Earth now you're familiar with the levels of organization of life on Earth atoms wake up molecules which make up macromolecules which make up cells Etc all the way up to the level of the whole biosphere and at every level we see what we call emergent properties these are features or behaviors of this level which do not appear at lower levels for example the heart is made up of cells such as cardiomyocytes but heart cells on their own cannot pump blood through the body they need to be organized in a particular way to have that property another example is that DNA is composed of subunits called nucleotides this is shown here in the molecular structure a single nucleotide cannot store genetic information but when many nucleotides are organized into a DNA molecule that molecule can store genetic information as we'll learn in this course life itself is an emergent property that occurs when matter is organized in a certain way we'll be studying the emergent properties of Life over the course of this entire semester