Evolution Flashcards
What is the starting point of reproduction according to cell theory?
All living organisms are composed of one or more cells which originate from pre-existing cells by the process of cell division.
What are the main reasons for cell division?
- Growth
- Repair of old/dead cells
- Reproduction
What is reproduction?
The process by which living organisms produce offspring of their own kind.
What are the two types of reproduction?
- Asexual (involves only one parent)
- Sexual (involves a combination of two parents)
What processes are involved in asexual reproduction?
Mitosis and cytokinesis.
What does mitosis accomplish?
The nucleus divides into two nuclei with identical genetic material.
List the importance of mitosis.
- Growth & development
- Asexual reproduction in some organisms
- Cell repair & replacement
- Copying & transfer of next generation nuclei/cells
- Maintaining the regular number of chromosomes in somatic cells
What is cytokinesis?
The process that completes cell division, separating the cytoplasm and organelles into two new daughter cells.
What are the two main parts of the cell cycle?
- Interphase
- Mitosis
What is interphase?
The preparatory stage that lasts from the end of one cell division to the beginning of the next.
What percentage of the cell cycle does interphase occupy?
About 90% of the time.
What occurs during the G1 phase of interphase?
The cell grows and prepares to replicate its DNA.
What happens during the S phase of interphase?
The chromosomes replicate, resulting in two identical copies called sister chromatids.
What occurs during the G2 phase of interphase?
Organelles and materials required for cell division are formed or replicated.
What are the five main phases of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What happens during prophase?
Sister chromatids become visible and the nuclear envelope breaks up.
What occurs during prometaphase?
Chromosomes gradually migrate to the center of the cell.
What is the arrangement of chromosomes during metaphase?
Chromosomes are lined up along the equatorial plate.
What happens during anaphase?
Centromeres are pulled apart, causing sister chromatids to separate into two daughter chromosomes.
What marks the beginning of telophase?
Separated chromosomes reach the opposite poles of the cell.
What is the final stage of the cell cycle?
Cytokinesis.
How does cytokinesis differ in animal and plant cells?
- Animal cells: cleavage furrow forms and deepens.
- Plant cells: a cell plate forms to divide the cell.
What happens to cells that do not divide in adult animals?
They exit G1 phase to enter an inactive stage called the quiescent stage (G0).