B3f - growth and development Flashcards
How are bacterial cells different from plant and animal cells(4)
Bacterial cells do not have a true nucleus
Do not have a mitochondria
Do not have chloroplasts
DNA is found in the cytoplasm as a single circular strand or chromosome
When are the phases of rapid growth for humans(2)
Just after birth(infancy)
During adolescence
Describe the main phases in a growth curve(5)
Infancy - first 2 years, rapid growth
Childhood - between infancy and puberty, steady growth
Adolescence - begins with puberty and continues until body development and growth are complete, rapid growth
Maturity/adulthood - between adolescence and old age, growth stops
Old age - between 65 and death
Explain the advantages and disadvantages of measuring growth by length(2)
Advantage - easy to measure
Disadvantage - only measures growth in one direction(doesn’t tell you about changes in width, diameter etc)
Explain the advantages and disadvantages of measuring growth by wet mass(2)
Advantage - easy to measure
Disadvantage - water content can vary and affect the result(e.g. plant is heavier just after rain, animal is heavier just after eating)
Explain the advantages and disadvantages of measuring growth by dry mass(2)
Advantage - measure the true growth of the whole organism without being affected by the amount of water
Disadvantage - need to kill the organism and dry it(unethical to do on humans)
Why may the growth of parts of an organism differ from the growth rate of the whole organism
Different parts of the organism may be needed at different times during the life of the organism
Describe stem cells(3)
They remain undifferentiated, which means they can develop into different types of cells, tissues and organs
Can be obtained from embryonic tissues
Could be used to treat medical conditions
Describe issues regarding stem cell research in animals(2 for + 1 against)
For - can treat life-threatening diseases;embryos used are unwanted ones from fertility clinics which would be destroyed anyway if not used
Against - embryos are destroyed during research which could have been potential human life
What are the difference between adult and embryonic stem cells(2)
Embryonic stem cells can form a greater range of cell types(more versatile)
Embryonic stem cells are easier to find since adult stem cells are only found in certain places(e.g. bone marrow)
How does plant growth differ from animal growth(4)
Animals tend to grow to a finite size but many plants can grow continuously
Plant cell division only happens in areas called meristems(at the tip of roots and shoots)
Plants gain height mainly through cells enlarging rather than dividing
Many plant cells keep the ability to differentiate but most animal cells lose it at an early stage
