BIO133 Week 7

Behavior

Observable response of an organism to internal or external stimuli

Behavioral ecology

Study of how behavior affects survival and reproduction

Stimulus

Internal or external signal that triggers a response

Innate behavior

Genetically programmed, does not require learning

Learned behavior

Modified by experience

Nature vs nurture

Interaction between genetic programming and environmental influence

Ethology

Study of biological basis of behavior

Fixed action pattern (FAP)

Innate, stereotyped behavior that runs to completion once triggered

Key stimulus (sign stimulus)

External cue that triggers a fixed action pattern

Innate releasing mechanism

Neural process that detects stimulus and triggers FAP

Eggshell removal (gulls)

Reduces predation → increases survival

Adaptive behavior

Behavior that increases fitness

Neuroethology

Study of neural basis of natural behavior

Internal signals

Hormones and neurotransmitters influencing behavior

Cortisol

Stress response

Epinephrine

Fight-or-flight

Norepinephrine

Alertness

Dopamine

Reward

Serotonin

Mood

Behavioral genetics

Study of genetic basis of behavior

Gene influence

Single genes can affect behavior (e.g., maternal care in mice)

Nonassociative learning

Change in response to one stimulus

Habituation

Decreased response to repeated stimulus

Associative learning

Linking stimuli or behavior with consequences

Classical conditioning

Association between two stimuli

Operant conditioning

Behavior modified by consequences

Reinforcement

Increases behavior

Punishment

Decreases behavior

Trial-and-error learning

Behavior shaped over time

Cognition

Ability to process information and solve problems

Cognitive learning

Problem-solving without direct trial-and-error

Tool use

Evidence of higher cognition

Optimality theory

Organisms behave to maximize benefits minus costs

Optimal foraging theory

Maximize energy gained while minimizing energy spent

Energy trade-off

Large prey = more energy but harder to obtain; Small prey = easier but less energy

Reproduction

Biological process of producing offspring

Asexual reproduction

Offspring from one parent, no fusion of gametes

Sexual reproduction

Fusion of sperm and egg → genetic diversity

Parthenogenesis

Development from unfertilized egg

Hermaphroditism

Organism has both male and female reproductive organs

Sequential hermaphroditism

Sex changes during life

Protogyny

Female → male

Protandry

Male → female

Genetic sex determination

XX/XY system

SRY gene

Triggers development of testes

Temperature-dependent sex determination (TSD)

Environment determines sex

ZZ/ZW system

Alternate chromosomal system (birds, reptiles)

External fertilization

Eggs and sperm released into environment

Internal fertilization

Sperm deposited inside female

Oviparity

Eggs develop outside body

Ovoviviparity

Eggs develop inside, no direct nourishment from mother

Viviparity

Offspring develop inside mother, nourished via placenta

Fish

Mostly external fertilization

Cartilaginous fish

Internal fertilization (claspers)

Amphibians

Mostly external, aquatic development

Reptiles

Internal fertilization, amniotic egg

Birds

Internal fertilization, oviparous

Mammals

Internal fertilization, live birth

Monotremes

Egg-laying mammals

Marsupials

Short gestation, develop in pouch

Eutherians

Long gestation, placenta nourishes embryo

Testes

Produce sperm

Seminiferous tubules

Site of sperm production

Epididymis

Sperm maturation and storage

Vas deferens

Transports sperm

Urethra

Passage for semen

Spermatogonium

Diploid stem cell

Primary spermatocyte

Undergoes meiosis I

Secondary spermatocyte

Haploid

Spermatids

Final haploid cells

Result of meiosis

4 sperm cells per meiosis

Head of sperm

Nucleus

Acrosome

Enzymes to penetrate egg

Midpiece

Mitochondria for energy

Tail (flagellum)

Movement

GnRH

Released by hypothalamus

FSH

Stimulates sperm production

LH

Stimulates testosterone production

Testosterone

Male traits + spermatogenesis

Inhibin

Inhibits FSH

Ovaries

Produce eggs

Fallopian tubes

Site of fertilization

Uterus

Site of embryo development

Cervix

Opening to uterus

Vagina

Receives sperm

Follicular phase

Follicles develop (FSH)

Ovulation

Egg released

Luteal phase

Corpus luteum forms

Estrogen

Builds uterine lining

Progesterone

Maintains uterine lining

hCG

Maintains corpus luteum during pregnancy

LH surge

Triggers ovulation

Menstruation

Shedding of uterine lining

Proliferative phase

Lining rebuilds

Secretory phase

Lining prepares for implantation

Fertilization

Sperm + egg → zygote

Implantation

Embryo embeds in uterus

Placenta

Nutrient exchange between mother and fetus

Contraception

Prevention of pregnancy

Barrier methods

Condoms, diaphragms