irreversible normal changes in a living organism as time passes
the same change is expected to occur in all members of a particular organism
e.g. growth in height, sexual maturation, graying of hair
Examples of developmental changes (4)
What are embryological changes? Give an example
Changes which occur before birth
e.g. formation of organs
What is maturation? Give an example
changes that result in the transformation of a child into an adult
geared to improve ability of a person to survive
e.g. strengthening of muscles
What is ageing?
Developmental changes that occur in later years
What is senescence?
progressive deterioration of physiogical function
Ageing vs senescence
everyone experiences ageing but not senescence
ageing and senescence are linked
e.g. ageing = change in amp; senescence = yellowing of the lens
The "working" definition of ageing is?
maturation consists of the progressive changes in size, shape and function during the life of an organism by which its genetic potentials (genotype) are translated into functioning mature systems (phenotype)
What is developmental biology?
the study of the genetic control of cell growth, differentiation and morphogenesis
carries instructions for synthesis of other compounds e.g. proteins, fats, carbohydrates and
how they should be assembled into appropriate structures to form a metabolically functioning body or soma
hereditary instructions passed from one generation to the next in genes
functioning organisms produced by the genotype
Define cell growth
increase in cytoplasmic volume in a cell
the increase in size or population of cells as in mitosis
the normal process by which a less specialized cell develops/matures to a more specific form and function
the biological processes that cause an organism to develop its shape
The term "genetic potential" encompasses?
recognition that development in many organisms may exhibit plasticity
the capacity of cells, organs and systems to change their function/state
the ability of one genotype to produce a range of different, relatively fit phenotypes in multiple environments
How is the phenotypic plasticity of development modified?
Through internal or external environmental conditions
Why have gene expression plasticity?
it is an evolutionary mechanism to match a phenotype suitable to surviving the envioronment
What are the two mechanisms by which directional selection of a trait in a population may be achieved?
gene expression plasticity
What are the three outcomes of directional gene expression?
aids fitness for the environment
negative effect on fitness
Features of gene expression plasticity
evolves very slowly
no env cue will be perfectly predictable of the presence of a particular stress so the fittest genotype in the long run will be one that does not completely commit to the presence of the stress
Benefit of adaptive phenotypic plasticity
ability to produce a better phenotype environment match for multiple environments
Limits to benefits of adaptive phenotypic plasticity
plasticity may result in a plastic organism exhibiting lower fitness to an environment
non-plastic organisms also suffer this same disadvantage
What are the limits to benefits of adaptive phenotype plasticity? (4)
variable reliability of env cues
developmental range limits
Variable reliability of env cues may result in?
expression of poor phenotype-env matching
What can occur as a result of lag-time limits?
poor phenotype-environment matching
The lag time limit is between?
sensing and responding to environmental cues
What has a shorter time lag than changes in morphology?
behaviour and physiology
What is the epiphenotype problem?
where traits that are expressed later may be weaker than a trait expressed earlier in development
What are the costs of adaptive phenotypic plasticity? (5)
information acquisition costs: process of sampling the env
Why does plasticity manifest? (2)
structural genes/products are directly affected by the external env OR
regulatory genes are affected by the enc and in turn affect the expression of structural genes
Reaction norm describes?
how a genotype reacts to the env to produce a range of phenotypes
How may the env affect development?
developmental plasticity scenario (most common)
high variable plasticity, strong genotype-env interactions
Draw how the env may affect development
In what stages is adaptive phenotype plasticity seen in vision science?
adulthood and ageing
Examples of types of ageing (3)
What is biological ageing?
ageing in the physical structures and functioning in the body
What is chronological/calendar ageing?
the passage of time since birth
What is cosmetic ageing?
changes in outward appearance with advancing age
roughly the number of years a person has lived
the temporal process of growing old
What types of definitions are there for senescence?
What is the individual definition of senescence?
the accumulation of harmful events that create a noticeable change in appearance or function in the course of ageing
What is the population-wide definition of senescence?
a progressive increase in the age-specific death rate even when the population is maintained under conditions that are ideal for survival underlined by a generalised deterioration ina broad spectrum of physiological and metabolic functions
the accumulation of the most severe senescent events
When are we mature?
peak physical performance
past peak performance
When does biological ageing begin? (6)
has too many illnesses
social role transition into grandparent
ability to recognise faces
computer gaming ability deteriorates
ability to run quickly
When does ageing begin? (3)
when homeostasis fails
loss of physiological aptitude after an organisms reached max repro capabilities
gradual decline in organ functional reserves --> reduces ability to maintain homeostasis under stress
Ageing is not ___________ but may ____________
predispose a person to disease in the presence of precipitating factors
When does senescence appear?
When cells, tissues and organs are not maintained
What does senescence do to an organism?
There is often a ____ in the appearance of _____ and the ______
commencement of failures in homeostasis
Why is there a delay in the appearance of age changes and the commencement in the failure of homeostasis?
The body has a large reserve capacity e.g. deterioration in accommodation
What is mitotic homeostasis?
when cells degenerate, they are regenerated
process to preserve functional integrity of tissues and organs
a balanced process in younger people
Why is degeneration not balanced by regeneration on older people?
telomere shortening and apoptosis
What are telomeres?
the ends of chromosomes
Chromosomes are involved in?
the replication and stability of DNA molecules
Why is there a failure in mitotic homeostasis?
shortened telomeres --> damaged DNA --> ceased function/damaged products
When do telomeres shorten and at what rate?
During DNA replication in somatic cells
100 base pairs per cell division
What are telomeres synthesised from?
the enzyme telomerase
Presence and rate of biological changes vary _____
Chronological/calendar age is only one contributing factor to ______
Why do we age or undergo senescence? (3)
unknown but reasons lie in 2 observations
force of natural selection is weaker at later stages i.e. after repro age, natural selection has less effect on genes
acquisition of longer longevity involves cost
Theories of senescence (7)
free radical theory
accumulated waste theory
cross-linking of collagen and other proteins
What theories are associated with the genetic basis of senescence?
anatagonsistic pleiotrophy hypothesis
developmental theory of ageing
What is the antagonistic pleiotrophy hypothesis? (2)
ageing is consequence of declining force of natural selection
traits that benefit young organisms can have detrimental effects on ageing phenotypes - escapes natural selection but leads to ageing
What is the developmental theory of ageing?
ageing process is the result of a developmental program that is active for the organisms entire lifespan
modification of gene expression from environmental influence can influence risk for disease, morbidity and mortality
What is the genetic clock?
cells can only divide by a number of times
locus of clock are the telomeres
What is the limited gene usage theory?
instructions in genes can only be read about 50x
errors accumulate and weakens body
What is the error catastrophe theory?
damage is not to genes but to RNA and protein molecules that read genes and carry out instructions
damaged molecules spread mistakes --> weakens body
What is the free-radical theory?
damage to DNA/protein/enzymes/body
from molecules with odd number of electrons which chemically reacts to other atoms to obtain complete electron pairs
build-up damage results in cell-death
What is the evidence against free-radical theory?
lack of correlation with species with longevity
antioxidants can be harmful rather than beneficial
long-lived mutants can have high levels of oxidative damage
What is the accumulated waste theory?
waste products accumulated from a loss of homeostasis --> obstructs normal cell activity
What is the the cross-linking of collagen and other proteins theory?
free radicals, glucose and light increases cross-linking --> inhibits normal cell function
What are the hormonal theories?
hormones are chemical messengers
hormone mediates ageing
What is the autoimmune theory?
ability of body to distinguish normal from foreign weakens
immune cells destroy own bodily components
What is the life history theory?
life span and reproduction cannot be max simultaneously through natural selection
resources are limited - fitness maximised by trading e.g. reproduction > homeostasis
ageing observed when loss of homeostasis > repair
Why do we die?
physiological decrements associated with senescence results in increased vulnerability to intrinsic and extrinsic factors and may cause death
Define ageing (5)
What is mortality
it is random
Mortality rate is not specific to the ___ but to the ____
Randomness in ageing must derive from randomness at 3 time points
end of life
At the beginning of life there is
inherent variability in the quality of the organism