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Cell Structure and Function

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Presentation on theme: "Cell Structure and Function"— Presentation transcript:

1 Cell Structure and Function
Part 2 Prokaryotes and Eukaryotes Characteristics of Living Things

2 Prokaryotes vs. Eukaryotes
Almost all the cells we have been learning about are from higher organisms like plants and animals. We call these ___________cells, meaning “true nucleus.” They are organized into different compartments (_________) including the nucleus, each with a different function. Many of these are separated from the rest the cell by their own ___________. There are TWO types of cells, though. Long before there were eukaryotes, there were much simpler organisms (usually single-celled) called ______________.

3 Early Life, Primitive Life
For the first ___________ years of Earth’s history, though, there were no organisms with eukaryote cells. In fact, most life consisted of very primitive (and usually single-celled) organisms. Some of these, such as the many types of bacteria and blue-green algae, still exist today. Their cells are much less complicated than eukaryote cells. _________________________. These types of cells are called ____________ cells, for “before nucleus”.

4 Prokaryote Cell Structure
Prokaryote cells are too small to see much structure under a normal microscope. We can see more detail with an _______ microscope, since that magnifies much more than light microscopes do. Prokaryotes do have a cell ___________, a _________, and cytoplasm, and they contain _______ (usually a circular chromosome) but they do not have a nucleus or organelles. They do much of the same chemistry as eukaryotic cells, but these functions are not in separate compartments. Most prokaryotic organisms are _______________. On average, they are _________ the size of eukaryote cells.

5 Prokaryote (bacteria) cell structure

6 Comparison of __________ and ___________ Cells

7 Examples Is yeast a eukaryote or prokaryote? How can you tell?
What about Cyanobacteria (aka blue-green algae)?

8 Comparisons Archaea (aka archaeabacteria) are a group of ______________ that in many ways are as different from the true Bacteria as they are from Eukaryotes. Many of them are found in ______________________, such as Yellowstone National Park’s hot springs, or deep ocean thermal vents. (Prokaryotes = ______________________)

9 Examples - True bacteria
Escherichia coli (E. coli) Under high magnification with a ________________ Under high magnification with an ______________

10 Streptococcus pneumoniae
Causes _____ infections Mycobacterium tuberculosis Causes __________

11 What is Life? Prokaryotes and eukaryotes are the two main divisions of life. But what is required for something to be alive? As a biological ___________ we can say living things: Are made of cells Can reproduce on their own Are based on a universal genetic code (DNA) Grow and develop Obtain and use materials and energy Respond to their environment Maintain a stable internal environment Change over time, when taken as a group

12 1. Living things are made of ____.
As we have seen, cells are the basic building blocks of life. We can break cells down to smaller parts, but those parts are not alive. Some organisms are a single cell by itself. These are unicellular (uni = _____) organisms. Others (like us) are multicellular (multi = _____), and may be made of billions of cells.

13 2. Living things ____________.
All living organisms produce new organisms through the process of reproduction. Most use __________________, where cells from two parents combine to form the new organism. In many cases, though, the new organism only has a single parent. This is called asexual (____________) reproduction. Offspring are copies of the parent. Examples of asexual reproduction: Bacteria __________ to form two new bacterial cells. Hydra budding (at left) A Hydra undergoing asexual reproduction. New buds (#3, above)

14 3. Living things are based on a universal genetic code.
Offspring always resemble their parents, so there is some way that information is _______________________________. That information is in the genetic code. The same code (with a few minor exceptions) is used for _____ living organisms. In cases of asexual reproduction, the offspring has the _____________ as the parent, so it is in many ways just a new copy of the parent. With sexual reproduction, the genetic code of the parents is mixed (_________) and the offspring is not identical to the parents. The offspring will share some traits with each parent, but will be _________. The genetic code is based on ________ (deoxyribonucleic acid) and _____ (ribonucleic acid). This essentially contains all the information needed to build a new organism. It is not only a program for what proteins are needed, but also when and how to make them.

15 4. Living things grow and develop.
All living things have a particular __________________________ that occurs over their lifetime – their life cycle. Some organisms _______________ without really changing over their lifespan. Many organisms start as a single-celled embryo and _______ (changing form, sometimes in several distinct stages) into an adult. As adults, they reproduce, and start a new generation. During development, cells not only get larger, but they ___________ (become different types, with different purposes).

16 5. Living things need materials and ________.
Growth and development require raw materials and energy. Plants get the raw materials they need from the soil and air, and get energy ____________ by photosynthesis. Animals get these materials by ________ on plants and other animals. They get energy by eating plants (or eating other animals that ate plants) that have stored the sun’s energy. The sun is the source of energy for almost all living things. Organisms break down or build up these materials by _________ processes known as metabolism.

17 6. Living things ________ to their environment.
All living things are exposed to a constantly changing _____________. Temperatures, sunlight, water, or other factors may change on an hourly, daily, or yearly cycle. All organisms respond in their own way to these changes. Many times, these changes may be important in the lifecycle of the organism. For instance, many plants require __________________ dark hours at night (or certain temperatures) before they will bloom. Many organisms may make __________ to their environment.

18 7. Living things maintain a stable ________ environment.
Despite constant changes in the external environment, the conditions on the inside of an organism need to _____ __________. It may take in water and food and eliminate waste, but the overall amount of water, overall temperature, etc., need to stay the same. This _________________________ to keep things stable is called homeostasis (“self-stable”). Most living things have a fairly ______ range of internal conditions they can tolerate. If homeostasis is disrupted too much, the organism may die. Frequently, external temperature, etc., are important only in how they affect the internal conditions.

19 8. Groups of living things evolve.
An organism changes as it ages, but the basic traits it inherited from its parents usually do not change. As a group, though, any kind of organism can _____________ _________ (evolve). From one generation to the next these changes are _____________________, but over hundreds or even millions of generations they add up to big changes. If the environment the organism is living in alters drastically, some may have changed in ways that allow them to survive and pass their traits on to future generations. Those that weren’t able to survive ________________. As an example: most of the plants we see in the Sonoran Desert did not originally develop in desert areas, but they were able to ___________________ to conditions when the climate changed and the desert arose. Some have changed enough that they don’t survive outside the desert.

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