BT101 Final Term Past Papers by Qamar

BT 101 Final Term Subjective

Q1. Define Survivorship curve. 2 Marks

Survivorship curve is one tool. It measures the proportion of individuals in a given species that are alive at different ages.

Q2. When Adaptation occurs? 2 Marks

Adaptation occurs when a change in a phenotype increases an animal’s chance of successful reproduction.

Change in environment is the force behind adaptations. It may result in the evolution of multiple new groups.

Q3. Function of Amnion in amniotic egg? 2 Marks

First vertebrates to possess amniotic eggs. Amnion protects embryo from desiccation, cushion the embryo, promote gas transfer, and store waste materials.

Q4. Factors that affect Logistic growth. 3 Marks

Environmental factors affect population growth.

• Climate
• Food
• Space
• Competition

Q5. Explain Fitness with examples. 3 Marks

Adaptedness or fitness: is a measure of the capacity for successful reproduction in a given environment. Not every characteristic is an adaptation to some kind of environmental situation. Neither adaptation leads to perfection. Genes of all traits are present in a population in form of alleles.

Examples:

Two phenotypes of toads

1. Green
2. Brown • Green leave average 4 offspring:
3. Brown leave average 2.5 offsprings.

• By custom, the most fit phenotype is assigned a fitness value of 1.0.

Q6. Characters of Nematoda? 5 Marks

• Triploblastic • Bilateral • Vermiform • Unsegmented • Pseudocoelomate • Complete digestive tract • Unique execratory system comprised of two or more renette cell • Body wall has only longitudinal muscles
• Cuticle may contain spines, bristle papillae and ridges • Pseudocoelom is a spacious fluid filled cavity • Visceral organs • Form hydrostatic skeleton • May be herbivores, carnivores, omnivores and saprotrophs • Feed on blood and tissue fluid of their hosts • Complete digestive tract • Excretion of nitrogenous waste • Ventral gland cells, called renette • Nervous system consist of anterior nerve ring.

Q7. Process of Decomposition. 5 Marks

Decomposition

1. Autolysis Breaking down of tissues by the body's own internal chemicals and enzymes
2. Putrefaction • Breakdown of tissues by bacteria. • release compounds such as cadaverine and putrescine causing decaying odor • Proteolysis releases nitrogen and phosphorous • Carbohydrate breakdown -

Aerobic by fungi and bacteria - Anaerobic by bacteria • Anerobic degradation of lipids • Nucleic acids and bones degradation.

Q8. Effects of Global Warming. 5 Marks

Arctic sea ice shrinking • Decrease in extent – 2.7% per decade since 1978 • Max. area of seasonally frozen ground decreased by 7% in Northern Hemisphere since 1900.

• Global sea level rise • Average rate of 1.8 mm per year (1961-2003) • Likely Sea level rise during the 21st century - 5 mm per year • Low lying areas, small island states may disappear, salt water intrusion into aquifers, floods • Low-lying coastal cities will be at the forefront of impacts

Non-polar glaciers • Widespread retreat during the 20th century

• Continental Precipitation • Significant increase in North & South America, northern Europe, north & central Asia • Drying in Mediterranean, southern Africa, parts of South Asia
• Extreme Weather • Frequency of drought, heat waves, typhoons, hurricanes and cyclones increased from 1960 until 2010. • Extremely wet or dry events within the monsoon period have increased since 1980.

Q9. Structure and Function of Golgi Apparatus. 5 Marks

Structure

• Located near the end of the ER close to the nucleus • Composed of several layers of cisternae (fluid-filled sacs) • Has three different parts: 1. cis-Golgi 2. medial-Golgi 3. trans-Golgi

Functions

• cis is first cisternae. • trans is final cisternae. • From trans, proteins are packaged into vesicles destined to lysosomes, secretory vesicles, or the cell surface. Transport vesicles are used to move back and forth between the ER and Golgi bodies • One side of the Golgi body receives transport vesicles produced by the ER. • This side is called cis face. • Opposite side releasing vesicle is trans face.