Flashcards in Growth Deck (12):
What rocks are fossils usually found in?
Rocks are usually found in sedimentary rocks.
Why do fossils help us?
Fossils help us trace the history and evolution of life. Fossils also provide evidence for Darwin's theory of natural selection.
Why don't fossil records show a continuous series of changes between ancestors and their descendants and why are there gaps?
- Most organisms decompose quickly when they die; not all of them find their way into an environment where they will be preserved and so only a small number of fossils form.
- Many fossils are yet to be found.
- Even if a fossil forms, it may not survive geological cycles.
What is the pentadactyl limb?
The pentadactyl limb is a forelimb with five "fingers" or "toes".
What has the discovery of pentadactyl limb lead scientists to believe?
The discovery of pentadactyl limb has led scientists to believe that all vertebrates directly descend from a common ancestor.
How is growth measured?
Growth is measured as an increase in an organism's size, length and mass.
What is the increase of growth a result of?
- Cell division - the number of cells increases
- Cell elongation - the length of cells increases
- Synthesis of organic materials (carbohydrates, proteins, fats and oils) - the mass of cells increases
How do plants grow?
- Plants grow throughout their life from cell division in tissues called meristems.
- Behind the meristems are regions where cells elongate and increase in size by water and other organic materials flowing into them.
- These cells are undifferentiated. As growth continues, differentiation of cells begins producing the types of cell that make up the tissues and organs of the plant.
How do animals grow?
- Cell division in animals occurs in all the tissues of the body.
- In young animals, tissues grow because cell division produces more cells than die through are or damage.
- Animals continue to grow until the gain of cells balances the loss of cells.
- Growth then stops, marking the start of becoming an adult. However, the mass of an individual may continue to increase as protein synthesis adds more mass to cells and the tissues that the cells form.
What do growth charts do?
Growth charts help parents and doctors to monitor children's development. The figures on the chart are different percentiles, each representing the spread of values for the characteristics selected. The 50th percentile represents the average value.
What are stem cells?