Essay questions Flashcards
Comparison of transport in humans and flowering plants
Structure of transport system
Similarities: two systems of vessels are involved
- Humans: blood vessels and lymph vessels
- Plants: xylem and phloem
Differences:
1.
- Humans: The lymph vessels join the veins near the neck
-Plants: Xylem and phloem are completely separated
2.
- Humans: Both blood vessels and lymph vessels consist of living cells.
- Plants: Xylem consists of dead cells and phloem consists of living cells
3.
- Humans: Blood vessels are elastic
- Plants: Xylem vessels are relatively rigid
4.
- Humans: valves are present in veins and lymph vessels
- Plants: Sieve plates are present in sieve tubes
Mechanism of transport
Similarities: a driving force is provided to move substances along the vessels
Differences:
1.
- Humans: the heart actively pumps blood around the body
- Plants: no special organ is developed to generate a driving force. Water is transported in xylem vessels mainly by transpiration pull
2.
- Humans: the elastic walls of arteries recoil to drive blood forward
- Plants: the walls of xylem vessels and sieve tube are inelastic and cannot recoil
3.
- Humans: Valves are present in veins and lymph vessels to prevent backflow of blood and lymph
- Plants: no special structures in xylem and phloem to prevent backflow of fluid
4.
- Humans: contraction of skeletal muscles surrounding the veins and lymph vessels squeeze blood and lymph forward
- Plants: no contraction of tissues in plants
Comparing mitotic and meiotic cell divisions
Prophase
- No pairing of homologous chromosomes
- No crossing over occurs
Prophase I
- Pairing of homologous chromosomes occurs
- Crossing over may occur
Metaphase
- Chromosomes line up along the equator
Metaphase I
- Pairs of homologous chromosomes line up along the equator
Anaphase
- Sister chromatids separate
Anaphase I
- Homologous chromosomes separate
Anaphase II
- Sister chromatids separate
Telophase, cytokinesis
- Two daughter cells are produced
- The daughter cells are diploid
- Daughter cells are genetically the same as the parent cell and as each other
Telophase II, cytokinesis
- Four daughter cells are produced
- The daughter cells are haploid
- Daughter cells are genetically different from the parent cell and from each other
SIgnificance of asexual and sexual reproduction
Asexual reproduction by vegetative propagation
Advantages:
- Desirable characteristics can be retained in the offspring
- No external agents are required
- allows rapid growth in population under favourable conditions
Disadvantages:
- Offspring show no genetic variations. The species is less adapted to the changes in the environment
- Overcrowding and competition of resources occur among offspring and parents
- Transmission of diseases from parents to offspring to parents is more likely
Sexual reproduction by producing flowers and seeds
Advantages:
- Offspring show genetic variations which may help the species adapt to changes in the environment
- Seeds can be dispersed over long distances to reduce overcrowding and competition of resources among offspring and parents
- Transmission of diseases from parents to offspring is less likely
Disadvantages:
- Desirable characteristics may not be retained in the offspring
- External agents are required for pollination, seed and fruit dispersal
- Occurs at a relatively slow rate
Comparison between sexual reproduction in humans and in flowering plants
Similarities:
1. Male gametes are small. This facilitates their transfer from the male sex organ to the female sex organ
2. Male gametes are produced in large numbers. This increases the chance of successful fertilization
3. Female gametes are larger and fewer in number
4. Female gametes are immotile and well protected in the parent body
5. Gametes are produced by meiotic cell division. This increases genetic variations
6. Embryos develop inside the body of the mother. They are well protected and nourished. This increases the chance of survival of the embryos
Differences:
1.
Flowering plants: male gametes are immotile
Humans: sperms are motile
2.
Flowering plants: external agents are involved in bringing the male and female gametes together. Pollen tubes are developed to transfer the male gamete to the ovule.
Humans: no external organs are involved. Sperms are transferred to and deposited in the female body through sexual intercourse
3.
Flowering plants: the offspring are dispersed away from the parent plants and become independent
Humans: the baby is provided with parental care after birth
Differences between reflex actions and voluntary actions
Nature of response
Reflex action:
- automatic, not under conscious control
- inborn
- stereotyped
Voluntary action:
- under conscious control
- not inborn
- not stereotyped
Nervous pathway
Reflex action:
- involves the spinal cord or the medulla oblongata, but not the cerebrum
- needs a stimulus and receptors are always involved
Voluntary action:
- involves the cerebrum
- may not need a stimulus and receptors are not always involved
Speed of response
Reflex action:
- always fast
Voluntary action
- usually slower
Difference between hormonal coordination and nervous coordination
Hormonal coordination / Nervous coordination
System involved: endocrine system / nervous system
Components of the system: endocrine glands, blood / neurones, nerves, brain, spinal cord
Nature of message: chemical / electrical and chemical
Route of transmission: along bloodstream / along neurones
Speed of transmission: slow / fast
Area of response: widespread / localized
Duration effects: long-lasting / short-lived
Importance: controls long-term processes / give rapid responses to changing conditions of the surroundings
