Introducing Individuals and Life Histories Flashcards
What is a unitary organism?
The form of this organism is determinate - programmed from birth
Easy to recognise and separate individuals
Strong programming means that local damage has serious consequences
What is a modular organism?
A genetic individual starts life as a single celled zygote but this doesn’t follow a set development programme
Growth occurs by repeated production of modules
Structure and programme of development is not predictable
Individual is not dead until all modules are dead - local damage is not important
What is a population?
A group of organisms of one species that interbreed and live in the same place at the same time
Why is the composition of a population important?
Properties of a population can affect population growth and resilience
What is the life history of a species?
The typical schedule of survival and reproduction, along with the traits that impact these patterns
What key traits underpin life history?
Rates e.g. somatic growth and senescence
Timing e.g. maturation and frequency of reproduction
Allocation e.g. offspring size and number
What are ephemeral species?
Plants and animals whose adult lifespan only lasts a few weeks or months
Desert annual plants
Some amphibia
What are ephemeral life histories an adaptation for?
Adaptation to living in highly variable, harsh environments
Wait out the bad times and take advantage of the rare ‘good’ conditions (usually < 8 weeks)
What are annual life histories?
Characterised by having one ‘generation’ per year
E.g. grow, flower, set seed and death all happen in less than a year
Spend part of the life dormant with a fraction emerging each year
What are annual life histories an adaptation for?
Seasonal environments - adapted to avoid harsh winter conditions
What are some ways to categorise life histories?
The frequency of reproduction e.g. iteroparous and semelparous
The seasonal timing of reproduction e.g. continuous or seasonal breeding
What is iteroparous reproduction?
Reproduction is spread out
Produce offspring during repeated reproductive episodes
Most mammals, majority of perennial plants and many insects
What is semelparity?
Large number of offspring produced in a single reproductive event after which the individual soon dies
Many annual plants, some perennial plants, many insects and a few vertebrates
What is continuous reproduction?
Reproduction is not tied to a particular season
Under the classification scheme of life histories, what can annual life histories be classified under?
They are seasonal breeders and are semelparous
What taxa come under seasonal breeders that are iteroparous? What is a difference between them?
Birds and many mammals
Mammals tend to have a longer juvenile phase
What animals come under continuous breeder that is iteroparous?
Humans and other primates
Tropical insects
What is the difference between life cycle and life history?
Life cycle is the development transitions an organism goes through over one generation
Life history is how organisms allocate energy to different functions affecting reproduction and survival over the life cycle
What is an organisms’ life history shaped by?
Natural selection
What is a Darwinian demon?
An organism that lives for hundreds for years, reproduces frequently and produces 1000s of offspring in each reproductive bout
What is the principle of allocation?
Each organism has a limited amount of energy that it can allocate for maintenance, survival, growth and reproduction
Energy allocated to one function is not available for another
Why can’t Darwinian demons exist?
Life histories are constrained by external factors (resources, competitors, predators etc) and trade-offs among life history traits
What are some trade-offs for life histories?
Intra-individual trade-offs:
* Reproduction vs survival
* Reproduction vs growth
* Reproduction vs condition
* Current reproduction vs future reproduction
* Number of offspring vs size of offspring
* Number of offspring vs survival of offspring
Inter-generational trade-offs (parent-offspring conflicts):
* Parental survival vs number of offspring
* Parental survival vs offspring condition
What happened to clutch size the following year when eggs were added or removed to the current clutch in Collard Flycatchers?
If eggs were removed from the current clutch, the clutch size the following year was increased
If eggs were added to the current clutch, the clutch size decreased the following year
