____
1. Describe and provide examples of
prezygotic and postzygotic reproductive
barriers.
Reproductive barriers prevent different
species from producing viable offspring and
ensure that fertilization and development do
not occur. Prezygotic barriers occur before
fertilization. Examples include temporal
isolation, where species reproduce at
different times; mechanical isolation, where
reproductive structures are incompatible; and
gametic isolation, where sperm cannot
fertilize the egg. Postzygotic barriers act after
fertilization has occurred. In these cases, the
hybrid offspring may fail to develop properly,
be weak, or be infertile. A common example
is the mule, which is a sterile offspring of a
horse and donkey.
1
____
2
____
2. Describe the function of
erythrocytes, leukocytes, platelets and
fibrin.
Erythrocytes, or red blood cells, are
responsible for transporting oxygen from
the lungs to tissues using hemoglobin.
Leukocytes, or white blood cells, play a
key role in immune defense by fighting
pathogens.
Platelets are involved in blood clotting by
gathering at injury sites.
Fibrin is a protein that forms a mesh to
stabilize clots and prevent excessive
bleeding.
3
____
3. Explain how the antagonistic hormones
insulin and glucagon regulate
carbohydrate metabolism.
Insulin and glucagon are antagonistic
hormones that regulate carbohydrate
metabolism by maintaining blood glucose
homeostasis. Insulin is secreted when blood
glucose levels are high. It reduces blood
glucose by promoting the uptake of glucose
into body cells and the breakdown of
glycogen in the liver, and stimulating the
storage of excess glucose as fat.
In contrast, glucagon is released when blood
glucose levels are low. It increases blood
glucose by stimulating the conversion of
glycogen into glucose in the liver and by
promoting the breakdown of fats and proteins
to produce glucose. Through these opposite
actions, insulin and glucagon work together
to keep blood glucose levels stable.
4
____
4. Explain the interaction between
hypothalamus and pituitary glands in males.
In males, the hypothalamus controls the
pituitary gland by releasing gonadotropinreleasing hormone (GnRH).
GnRH stimulates the pituitary to secrete
luteinizing hormone (LH) and follicle-stimulating
hormone (FSH).
These hormones regulate testosterone
production and spermatogenesis in the testes.
5. List and describe the functions of
hormones released by the ovary and testes.
The ovaries release estrogen and
progesterone, which regulate the menstrual
cycle, ovulation, pregnancy, and female
secondary sexual characteristics.
The testes release testosterone, which
controls sperm production, male reproductive
organs, and male secondary sexual
characteristics.
5
____
6. Distinguish between morphogenesis,
differentiation, and growth.
Morphogenesis is the process by which
tissues and organs acquire their shape.
Differentiation is the process in which cells
become specialized in structure and function.
Growth refers to an increase in cell size or
number during development.
7. Compare the growth of a plant in darkness
(etiolation) to the characteristics of greening
(de-etiolation).
Etiolation occurs when plants grow in the
absence of light, resulting in elongated stems,
small leaves, and pale color due to low
chlorophyll.
De-etiolation occurs when plants are exposed
to light, leading to shorter stems, expanded
leaves, and green coloration due to chlorophyll
production.
6
____
8. Distinguish between conservation
biology and restoration biology.
Conservation biology focuses on
protecting intact or threatened
ecosystems to preserve biodiversity and
prevent species extinction.
It mainly involves protection,
management, and reducing human
impacts and usually requires lower cost.
In contrast, restoration biology focuses
on repairing damaged or degraded
ecosystems and returning them to their
original state.
It requires active human intervention,
such as reforestation and species
reintroduction, and is often costly and
labor-intensive.
7