Chapter 2 Section 1: What is life? Key Concepts Cell What characteristics do all living things share? Unicellular Multicellular Where do living things come from? Stimulus Response What do living things need to survive? Development Key Terms (write with enough space to answer them in your ISN): Spontaneous generation Autotroph Heterotroph Organism Homeostasis

UGGGH That’s so many key tterrrrrrms ugggggggh I know. Write them down  you do need to know them all.  sorries.

Characteristics of Living Things What do you know about living things? What do living things have in common? What is the difference between a wind-up toy and a living thing? All living things have a cellular organization, contain similar chemicals, use energy, respond to their surroundings, grow and develop and reproduce. Organisms – living things

Characteristics of Living things, cont. Cellular Organization Chemicals of Life Energy Use Response to Surroundings Growth and Development Reproduction (By the end of the section, you should be able to list all of the characteristics of living things as well as explain them.)

What is life? Cellular Organization Cell Chemicals of Life Water Basic unit of structure and function in an organism Water Most abundant Carbohydrates Unicellular Energy sources Single-celled organisms Proteins and lipids Includes bacteria Building materials Multicellular Nucleic acids Composed of many cells Genetic material

What is life? Response to surroundings Reproduction Growth and Development Production of offspring similar to the parents Stimulus (pl. stimuli) – a change that causes an organism to react Development – process of change to become more complex This is how new living things are created Response – an action or change in behavior NOT spontaneous generation, which is a mistake

Redi and Pasteur’s Spontaneous Generation Experiments in brief Redi’s experiment: 1600s, Italian doctor Francesco Redi Helped disprove spontaneous generation Jars with meat Covered jar drew no flies/maggots Uncovered had maggots Redi reasoned flies laid eggs on the meat Pasteur’s experiment: Mid 1800s French chemist Demonstrated that new bacteria appeared in broth only when they were produced by existing bacteria Clear broth into two flasks; one was boiled to kill bacteria Unboiled broth became cloudy, indicating bacterial growth

Life comes from Life Living things come about from reproduction Not spontaneous generation – the idea that living things can come from nonliving sources Redi’s experiment Summed up: Rotting meat does not produce flies Pasteur’s experiment Summed up: New bacteria only appeared in broth when they were produced by existing bacteria These experiments were important because they showed evidence against spontaneous generation

Redi’s Experiment (more in depth) Italian doctor in the 1600s who designed an experiment to show that flies to not arise from decaying meat. My wig is the least interesting thing about me.

Redi’s experiment Place meat in identical jars Leave one jar uncovered, cover one jar with a cloth that let in air After a few days, maggots accumulated in the open jar on the meat Redi reasoned that flies had laid eggs on the meat in the open jar. Eggs hatched into maggots Tada.

Okay, so, let’s think about Redi’s experiment in terms of what we know about experiments How do we design an experiment? Pose questions, hypothesis, collect and interpret data, communicate results. So, what was Redi’s question? What was his hypothesis? What data did he collect? What did he think it meant? What variables did Redi have? How did he control other variables?

Pasteur’s experiment (more in depth) 1800s French chemist Did some other great germ-theory stuff from which we now have Pasteurization

The experiment Pasteur put clear broth into two flasks with curved necks Necks let oxygen in but kept out bacteria Boiled the broth in flask 1, but not the other (flask 2) Killed bacteria in flask 1 In a few days, the unboiled broth (flask 2) became cloudy (indicating presence of bacteria) Boiled broth was still clear (flask 1)

Pasteur’s experiment Remember that the necks of the flasks prevented new bacteria from entering. At this point, we understand that: 1. Boiling the broth in flask 1 killed the bacteria already present, no new bacteria could enter, so the broth remained clear (without bacteria) 2. The unboiled broth had bacteria present, even though no new bacteria could enter, the existing bacteria reproduced and made the broth cloudy Later, Pasteur took the still-clear broth (flask 1) and broke the neck of the flask. Bacteria from the air could now enter and the broth became cloudy.

Pasteur’s experiment, analyzed: What was Pasteur’s hypothesis? What were his variables? What did he have to control to ensure the validity of the experiment? What does this tell us about the need for controlled experiments? Write the questions and your answers in your ISNs with a partner

The Needs of Living Things All living things need water, food, space, and stable internal conditions Stable internal conditions?? Organisms keep homeostasis (maintenance of internal conditions) What are some examples of homeostasis? Autotrophs vs. heterotrophs Autotrophs make their own food (self-feeder) Heterotrophs eat other organisms

What you should know from this section: Key terms The 6 characteristics of living things What livings things need to survive Don’t forget: water, food, living space, and stable internal conditions. The experiments were just some background info for you, they won’t be on the test 