Growth And Development Flashcards
Describe how to make a stained slide of an onion cell
- use tweezers to peel a thin layer of skin tissue from an onion
- place the onion tissue onto a microscope slide on top of distilled water
- add a drop of iodine solution to the tissue and carefully cover the slide
- you should be able to see the parts of an onion cell at X100 magnification
What is growth measured as?
An increase in height, wet mass or dry mas
Describe the process of growth as cell division followed by cells becoming specialised
The cells specialise or differentiate at an early stage into different types of cell to form tissues and organs. All parts of animals grow, but growth eventually stops
When do animals and plants grow?
Animals grow in the early stages of their lives whereas plants grow continually
Understand that all parts of an animal are involved in growth whereas plants grow at specific pars of the plant
Animals - all parts are involved in growth
Plants - grow at specific parts of the plant
Describe the difference between the arrangement of DNA in a bacterial cell and a plant/animal cell
Plant cells keep their DNA inside the nucleus but bacterial cells do not have a nucleus so their DNA floats as circular strands
What do bacterial cells lack?
A ‘True’ nucleus
Mitochondria
Chloroplasts
What is the best measure of growth?
Dry mass as it is the most accurate method
Describe the main phases of a typical growth curve
Growth in organisms usually follows a typical ‘s-shaoed’ pattern
Identify the rapid growths in humans
In human growth there are two phases of rapid grwoth, one just after brith and the other in adolescence
Explain the advantages and disadvantages of measuring growth by:
- Length
- Wet mass
- Dry mass
L - easy and rapid measurement. Increase in mass might occur with no increase in length
WM - quite easy to measure. Water content of living tissue can be very variable and may give a distorted view overall
DM - most accurate method. Destructive as removal if water kills organisms
Explain why the growth of parts of an organism may differ from the growth rate of the whole organism
This is because the circulation of blood is vital to the growth and development of the embryo and therefore needs to be prioritised
Explain the difference between adult and embryonic stem cells
An embryonic cell can develop into any cell in the body without limit to replenish. And an adult cell is only able to mature into a specialised tissue cell from which tissue the cell is positioned
Explain why plant growth differs from animal growth
- animals tend to grow to a finite size but many plants can grow continuously
- plant cell division is mainly restricted to areas called meristems
- cell enlargement is the main method by which plants gain height
- many plant cells retain the ability to differentiate but most animal cells lose it at an early stage
Discuss issues arising from stem cell research in animals
- embryos have the potential to become a human being, so it is wrong to experiment on them
