Download Endosymbiosis Questions KEY Endosymbiosis Questions KEY

Endosymbiosis Questions KEY
1. What was Jeon’s hypothesis for why the surviving amoeba with the x-bacteria still within them
were surviving rather than dying off the way the majority of the original population of amoeba did?
THE BACTERIA MAKE A PROTEIN THAT THE AMOEBA NEED TO HAVE TO SURVIVE (AND CAN’T
MAKE THEMSELVES).
2. Give at least two examples that show the amoeba and the x-bacteria were still considered
separate organisms. (ANY 2 OF THESE)
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THEY DIVIDE ON THEIR OWN
NEED TO PROVIDE THEIR OWN ENERGY (FOOD) SOURCES
USE THEIR OWN GENES FOR REPRODUCTION
 MAKE THEIR OWN PROTEINS
3. What are the three domains of living organisms that we see around us today? (NEED ALL 3)
 ARCHAEA
 PROKARYOTE
 EUKARYOTE.
4. What type of domain is virtually all life around us today? EUKARYOTE
5. How long ago did the first eukaryotic cells form? ABOUT 1 BILLION YEARS AGO (BYA) When
do scientists think the very first cells formed on Earth (look back on page 1)? ABOUT 3.8 BYA
6. What are three characteristics of prokaryotic cells? (ANY 3 OF THESE)
 NO NUCLEUS—HAS CIRCULAR DNA STRAND
 HAS A CELL WALL & CELL MEMBRANE
 NO INTERNAL MEMBRANE BOUND ORGANELLES
 TINY
 SIMPLE
7. What are three characteristics of eukaryotic cells? (ANY 3 OF THESE)
 DNA IS LINEAR, IN THE SHAPE OF A DOUBLE HELIX AND FOUND IN THE NUCLEUS
 HAS INTERNAL MEMBRANE BOUND ORGANELLES
 VERY COMPLEX
 CAN BE EITHER SINGLE CELLED ORGANISMS OR MULTI-CELLED ORGANISMS
 HAS MITOCHONDRIA TO PROVIDE ENERGY FOR THE CELL
8. If “ancient” mitochondria migrated into a host cell (similarly to Jeon’s amoeba and x-bacteria) what
was a benefit to the host cells and to the “ancient” mitochondria?
 THE SYMBIOTE BENEFIT: PROTECTED ENVIRONMENT, EASE OF OBTAINING FOOD, ETC.
 THE HOST COULD BENEFIT BY GAINING AN “ALWAYS ON” ENERGY SOURCE.
Endosymbiosis Questions KEY
9. Explain the three pieces of evidence for endosymbiosis.
 BOTH THE CELL AND MITOCHONDRIA REPRODUCE ON THEIR OWN CYCLES AND
SEPARATE FROM EACH OTHER
 THE CELL AND THE MITOCHONDRIA HAVE DISTINCTLY DIFFERENT DNA
 THE MITOCHONDRIA HAS A DOUBLE MEMBRANE (LIKE A CELL’S PLASMA MEMBRANE).
10. Which happened first, mitochondria or chloroplasts? Why?
MITOCHONDRIA HAPPENED FIRST. WE KNOW BECAUSE THEY ARE FOUND IN ALL
EUKARYOTIC CELLS WHILE CHLOROPLASTS ARE ONLY FOUND IN PLANTS.
11. Why are chloroplast thought to have been free-living bacteria before joining with (what would
become) plant cells?
ALL THE MANY SIMILARITIES BETWEEN THESE TWO ORGANELLES (BOTH MEMBRANE BOUND,
BOTH DIVIDE ON THEIR OWN SCHEDULE, BOTH HAVE OWN DNA).
12. Why couldn’t mitochondria or chloroplasts go back to being free-living cells now? Back up your
answer with information from the article?
NO THEY CAN’T BE FREE-LIVING CELLS AGAIN. THE ARTICLE STATES KEY PROTEINS THAT
THE MITOCHONDRIA NEED ARE NOW MADE IN THE CELL AND IMPORTED (THE GENES FOR
MAKING THOSE PROTEINS WERE TRANSFERRED TO THE CELL’S NUCLEUS
13. What does the theory of endosymbiosis explain?
IT EXPLAINS HOW ONCE FREE-LIVING PROKARYOTES MAY HAVE MOVED INTO ANOTHER CELL
CREATING A NEW TYPE OF CELL—THE EUKARYOTE.
14. What other structures found in eukaryotic cells could be explained by endosymbiosis?
ANY OF THE MEMBRANE BOUND ORGANELLES FOUND IN EUKARYOTIC CELLS LIKE
LYSOSOMES, GOLGI APPARATUS, ETC.