Exploring & Classifying Life

1. Exploring & Classifying Life Chapter 1

2. What is Life? • All living things are called organisms • Organisms must meet certain requirements • All living things are organized • Organisms are organized by cells • A cell is the smallest unit of an organism that carries on the functions of life. • Each cell has an orderly structure and contains hereditary material (DNA)

3. What is Life? • All living things respond to their environment • This means they can respond to a stimulus • A stimulus is anything that causes some change in an organism • I.e., heat, pain, sunlight • A response is the way an organism reacts to a stimulus • I.e., sweat, move away, grow towards light • Homeostasis is the maintaining of proper conditions inside an organism • Keep temperature, ph, mineral levels, etc. relatively constant

4. What is Life? • Living things take in and use energy • Three different ways: • Producers perform photosynthesis and get energy from the sun • Some producers perform chemosynthesis and get energy from chemical sources • Consumers perform respiration and get energy from their food

5. What is Life? • Living things grow and develop • Growth of multicellular organisms is due to an increase in the number of cells • Growth of unicellular organisms is due to an increase in the size of the cell • Development involves any changes that take place during the life of an organism

6. What is Life? • Living things reproduce • Reproduction can be either sexual or asexual • Sexual reproduction is when two reproductive cells unite • Ex: pollen and egg • Asexual reproduction is when one organism either splits or makes a copy of itself • Ex: bacteria and binary fission

7. What Do Living Things Need? • Living things need a place to live that provides for all of the organism’s needs • Called a habitat • Living things need raw materials, like water, proteins, fats, and sugars • Used for food, energy, building blocks for new material

8. Review Questions • What is the main source of energy used by most organisms? • List 5 traits most organisms have. • Why would you expect to see cells if you looked at a section of a mushroom cap under a microscope? • In order to survive, what things do most organisms need? • Why is homeostasis important to organisms? • What are the similarities and differences between a goldfish and the flame of a burning candle? • Which characteristic of life is essential for a species, but not for an individual organism?

9. Spontaneous Generation • The early theory that living things could come from nonliving things • If you left out food, maggots, flies, etc. would appear - no knowledge of “little things.” • Was replaced by the theory of biogenesis • Living things can only come from other living things • Why was this replaced you say? • I’m glad you asked!

10. A Little History • Francesco Redi (1668) • Put decaying meat in some jars, then covered half of them. When fly maggots only appeared on uncovered meat, concluded they came from fly eggs, not from the meat. • John Needham (1745) • Heated broth in sealed flasks. Broth became cloudy with microorganisms - concluded that they came from spontaneous generation

11. A Little More History • Lazzaro Spallanzi (1768) • Broiled broth in sealed containers for longr than Needham. Only containers that were opened became cloudy. • Louis Pasteur (1859) • “Disproved spontaneous generation by boiling broth in S-necked flasks that were open to the air. The broth became cloudy only when a flask was tilted and the broth was exposed to dusk in the S-neck.” Glencoe, p.22

12. Alexander I. Oparin (1924) • Hypothesizes that gases in Earth’s early atmosphere combined to form more complex compounds found in living things • With help from the Sun, lightning, and geothermal energy, they combined • The original gases were: • Ammonia • Hydrogen • Methane • Water vapor • New compounds washed into ocean and formed “primordial soup.”

13. Stanley L. Miller andHarold Urey • Tested Oparin’s hypothesis • Showed that chemicals found in living things can be produced artificially • They sent an electric current through a mixture of gasses (ones mentioned previously) • When they cooled, they condensed into the hypothesized “primordial soup.” • Contained amino acids

14. Review Questions • What’s the difference between spontaneous generation and biogenesis? • Describe 3 experiments that helped disprove spontaneous generation. • What were the results of the Miller-Urey experiment? • Why was Oparin’s hypothesis about the origins of life important to Miller and urey? • It was thought that in Spallanzi experiment, some “vital force” in the broth was destroyed. Was it? Explain. • Hypothesize why Needham probably concluded that spontaneous generation occurred.

15. Aristotle • Greek philosopher • First to classify organisms • Two groups • Plants and Animals • These groups were split up further • Ex: Animal group was split into four legs, fewer legs, blood, no blood, etc.

16. Carolus Linnaeus • Introduced a system based on similar structures of organisms • Came up with the most commonly used classification system • Kingdom (humans - Animalae) • Animalae, Plantae, Fungi, Protista, Monera • Phylum (humans - Chordata) • Class (humans - Mammalia) • Order (humans - Primata) • Family - (humans - Homonidae) • Genus (humans - Homo) • Species (humans - sapiens) • Organisms in the same species can mate and produce fertile offspring

17. Modern Classification • Modern systems are based on phylogeny • Phylogeny is the evolutionary history of an organism • The same divisions are used (Kingdom, Phylum, etc.), some animals are just put into different places • Now there are 6 (some would say 8) kingdoms • Animal, Plant, Fungus, Protist, Eubacteria, Archaebacteria • Some split protist into animal-like protists, plant-like progists, and fungus-like protists

18. Binomial Nomenclature • Two-word system used by Linnaeus to name species • Homo sapiens • The first word identifies the genus, or group of similar species • Always capitalized, italicized when typed, underlined when written • Homo • The second word identifies the species • Always lower-case, italicized when typed, underlinen when written • sapiens

19. Why Use Scientific Names? • Avoid mistakes - common names can be misleading • It’s also a universal language • Show that organisms in the same genus are related • Ex: • To give descriptive information • The names mean something (in some language) • To allow information to be organized easily

20. Tools for Classification • Field Guides - descriptions and illustrations of organisms • Dichotomous keys - detailed lists of identifying characteristics that include scientific names • Example in Book (some mice of North America):

21. Review Questions • What is the purpose of classification? • What were the contributions of Aristotle and Carolus Linnaeus to classification of living things? • How can you identify a species using a dichotomous key? • Would you expect a field guide to have common names as well as scientific names? Why? • Why can common names cause confusion? • Think of a quick dichotomous key to help identify the people next to you.