Warm Up 3/27

1.     Define the terms stimulus, response, and reflex in the context of behavior

·       Stimulus:  A change in the environment (external or internal) that is detected by a receptor

·       Response:  A change in an organism (an action) resulting from a stimulus

·       Reflex:  A type of response that is rapid and involuntary (unconscious)

2.     Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the response of animals to stimuli

·       Receptors transform stimuli into electrical nerve impulses

·       Sensory neurons relay the nerve impulse to the central nervous system (via the dorsal root of the spinal cord)

·       Relay neurons (also called interneurons or connector neurons) transmit nerve impulses within the CNS

·       Motor neurons receive nerve impulses from the CNS (via the ventral root) and relays the signal to an effector

·       Effectors (muscles or glands) produce a response to the stimulus

·       Synapses are the junctions between two nerve cells and transmission of a signal across these junctions require chemical neurotransmitters

3.     Draw and label a diagram of a reflex arc for a pain withdrawal reflex, including the spinal cord and its spinal nerves, relay neuron, motor neuron and effector

4.     Explain how animal responses can be affected by natural selection, using two examples

Natural selection describes the process by which the frequency of an inheritable characteristic changes as a result of external (environmental) agents

These beneficial inheritable traits (adaptations) can include instinctive behaviours such as migrating, foraging, hunting, communication, etc.

Example:  Blackcap Migration Patterns

§  The blackcap (Sylvia atricapilla) exhibits behavioural variation in its migration patterns from its summer breeding grounds in Germany

§  Historically, most blackcaps migrated south to Spain (warmer climate in winter) with a minority migrating west to the UK (closer, but cooler)

§  With a rise in global temperatures, more blackcaps are now migrating west to the UK (more favourable survival prospects increase allele frequency)

Example:  House Sparrow Feeding Behaviours

§  The house sparrow (Passer domesticus) will chirp and gape as a fledgling in order to be fed by its parents

§  In a nest of chicks, those which chirp louder and gape more obviously are more likely to be fed more and survive longer

§  Hence the alleles responsible for chirping and gaping are passed to offspring increasing prevalence of the behaviour

Warm Up 2/28

1. What are the steps in oogenesis?

• Oogenesis describes the production of female gametes (ova) within the ovary
• The process begins during foetal development, when a large number of cells (oogonia) are formed by mitosis before undergoing a period of growth
• These cells begin meiosis but are arrested in prophase I until puberty
• At puberty, some follicles continue to develop each month is response to FSH secretion
• These follicles complete the first meiotic division to form two cells of unequal size
• The cell with less cytoplasm is a polar body (which degenerates), while the larger cell forms a secondary oocyte
• The secondary oocyte begins the second meiotic division but is arrested in prophase II (until fertilisation)
• It is released from the ovary (ruptured follicle develops into corpus luteum) and, if fertilisation occurs, will complete meiosis
• The second meiotic division will produce an ovum and a second polar body

Overview of Oogenesis

2. What are the steps in spermatogenesis

• Spermatogenesis describes the production of spermatozoa (sperm) in the seminiferous tubules of the testes
• The first stage of sperm production requires the division of germline epithelium by mitosis
• These cells (spermatogonia) then undergo a period of growth
• This is followed by two meiotic divisions that result in four haploid daughter cells
• These haploid cells then differentiate to form sperm cells
• The developing sperm cells are nourished throughout by the Sertoli cells

Overview of Spermatogenesis

3. What are the similarities and differences between the two?

Similarities:

• Both processes result in the formation of haploid gametes
• Both processes involve mitosis, growth and meiosis

Differences: