24 Questions
What is a characteristic of an annual species?
It completes its life cycle in 12 months or less
What type of life cycle is characterized by one reproductive event followed by death?
Semelparous
Which type of organism has discreet, non-overlapping generations?
Annual
What is a key difference between semelparous and iteroparous species?
The number of reproductive events
Which type of life cycle is characterized by an organism that persists for many growing seasons?
Perennial
What is a characteristic of an iteroparous species?
It has multiple reproductive events in its lifetime
What is a key difference between continuous and overlapping life cycles?
The duration of their life cycle
Which type of life cycle is characterized by an organism that may or may not overwinter as a non-seed or non-egg?
Annual
What is a characteristic of a semelparous individual?
It has only one reproductive event during its lifetime.
What is a key difference between annuals and perennials?
Annuals complete their life cycle in 12 months or less, while perennials persist for many growing seasons.
What is a characteristic of an iteroparous individual?
It has multiple reproductive events during its lifetime.
What is an example of an overlapping semelparous life cycle?
A species that has multiple generations that overlap in time.
What is a characteristic of continuous iteroparous species?
They have a long lifespan with seasonal breeding.
What is a key difference between semelparous and iteroparous individuals?
Semelparous individuals die after one reproductive event, while iteroparous individuals have multiple events.
What is a characteristic of perennial life cycles?
They have a long lifespan with multiple breeding seasons.
What is a key difference between annuals and perennials in terms of energy investment?
Annuals invest more energy in reproduction, while perennials invest less.
What is a characteristic of semelparous organisms?
They have a single reproductive event during their life, then die.
What is the primary difference between annual and perennial life cycles?
The duration of their life cycle.
In terms of energy investment, what is a key difference between semelparous and iteroparous organisms?
Semelparous organisms invest more energy in reproduction, while iteroparous organisms invest less.
What is the result of the trade-offs between life history traits?
Optimization of survival.
What would be the characteristics of a 'Darwinian Demon'?
It would live forever and produce many offspring continuously.
What is the key assumption underlying life history theory?
There are trade-offs among life history components.
What is the result of constraints on life history strategy?
Shaping of life history strategy.
What determines an organism's Darwinian fitness?
The combination of life history traits.
Study Notes
Life Histories
- Life histories are the combination of characteristics that define an organism's life cycle
- Main types of life cycles include:
- Annuals vs perennials
- Semelparous vs iteroparous
Semelparous vs Iteroparous
- Semelparous: individual has one single reproductive event during its life, then dies
- Iteroparous: individual may have many reproductive events (during season or life)
- Invests large amount of energy in reproduction vs invests lesser proportion of resources in reproduction
Overlapping vs Continuous
- Overlapping semelparous: generations overlap, but still die after reproduction
- Overlapping iteroparous: multiple reproductive events, but with overlap between generations
- Continuous semelparous: continuous reproduction, but still dies after reproduction
- Continuous iteroparous: continuous reproduction with multiple events
Annuals vs Perennials
- Annuals: complete life cycle in 12 months or less
- May or may not overwinter as non-seed/egg
- Perennials: persist for many growing seasons
- One part of the organism dies/gets absorbed and regrows from the following season
Life History Traits
- Measurable characteristics or attributes that affect survival and reproduction
- Examples:
- Size at birth
- Growth rate
- Age/size at maturity
- Number and size of offspring
- Age/size-specific reproductive investments
- Age/size-specific mortality schedules
- Lifespan
- The combination of traits determines Darwinian fitness
Life History Theory
- Key assumption: there are trade-offs among life history components
- "Reproduction is costly, and so is growth" – Trade-off
- Constraints shape the life history strategy of species
- Examples of constraints include:
- Limited resources
- Environmental pressures
- Predation
- Optimization of survival and reproduction is favored by selection
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