Podcast
Questions and Answers
What is the primary limitation that affects the trade-off between egg number and reproductive seasons?
What is the primary limitation that affects the trade-off between egg number and reproductive seasons?
What strategy does natural selection favor in the context of reproduction and survival?
What strategy does natural selection favor in the context of reproduction and survival?
What is the result of allocating too much energy to egg-laying according to the content?
What is the result of allocating too much energy to egg-laying according to the content?
Which of the following best describes the relationship between fecundity and survivorship in populations?
Which of the following best describes the relationship between fecundity and survivorship in populations?
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Which reproductive strategy might lead to fewer descendants but increased individual survival?
Which reproductive strategy might lead to fewer descendants but increased individual survival?
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What characterizes the parental investment in orchid seeds compared to elephants?
What characterizes the parental investment in orchid seeds compared to elephants?
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What is a key difference between the reproductive strategy of mice and that of elephants?
What is a key difference between the reproductive strategy of mice and that of elephants?
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In terms of parental investment, what is true about the coco-de-mer seed?
In terms of parental investment, what is true about the coco-de-mer seed?
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How do the offspring survival strategies of different species contrast?
How do the offspring survival strategies of different species contrast?
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What factor directly influences the number of reproductive seasons for a species?
What factor directly influences the number of reproductive seasons for a species?
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Study Notes
Instructor Information
- Instructor: Dr. Sam Yeaman
- Office hours: Wednesdays 4-5pm BI 394
- Email: [email protected] (subject: BIOL 241)
Research Interests
- Research aims to understand how organisms adapt to their environment.
- Research questions include: Is evolution flexible? How do different species respond to the same environmental challenges?
Research Methods
- Use computer simulations, genome sequence data, and statistical modeling.
Upcoming Assignments
- Lecture Assignment 4, next Wednesday, November 27
- Topic 10: Reproduction
- Bring a response form!
Biology 241 Overview
- Course covers energy flow in biological systems.
- Units include: molecular energy transformations, cellular energy transformations, energy allocation in organisms (energy budgets, thermoregulation, locomotion, and reproduction), and energy flow in ecosystems.
- Relevant chapters are 26.1-26.4 and 26.7b.
Learning Objectives
- Explain why energy is needed for growth, repair, and reproduction.
- Define life history and explain how life history strategies vary among species.
- Identify and describe the three types of survivorship curves.
- Explain life-history trade-offs and interpret data in terms of costs, benefits, and trade-offs between current reproduction and other energy uses.
Reproduction
- Asexual reproduction creates clones (exact copies).
- Prokaryotes reproduce via binary fission.
- Some eukaryotes (protists, fungi, and some plants) reproduce via mitosis.
- Sexual reproduction creates recombinants (combined genomes).
- Replicated genomes are halved into gametes (sperm and eggs) and combined to produce a zygote.
- Only occurs in eukaryotes.
Life History Traits
- Variable traits include growth rate, parental investment, number of offspring (fecundity), frequency of reproduction (parity), size/age at sexual maturity, size of offspring, and longevity/life expectancy (mortality rate).
Trade-offs
- 2 life-history traits competing for limited resources make simultaneous maximization impossible.
- Example - seed size vs seed number.
Growth
- Indeterminate growth: growth continues throughout the lifespan (ectotherms - reptiles, fish, plants, etc).
- Determinate growth: growth ceases when the "adult" stage is reached (endotherms - birds, mammals).
Active vs. Passive Care
- Passive care: energy investment before birth (seed development, gestation, etc).
- Active care: energy investment after birth (raising offspring).
Predation and Life History Traits
- Predation affects life history traits in Trinidadian guppies and pike cichlids.
- Higher elevations = fewer predators, larger guppies at reproduction
- Lower elevations = more predators, smaller guppies at reproduction
Lifespan
- Study of lifespan in nematodes (daf-2 mutants, wild-type comparison).
- Why don't organisms live forever in the same environment?
Parity
- Semelparity: organisms breed only once in their lifetime (e.g., Pacific salmon).
- Iteroparity: organisms breed more than once in their lifetime (e.g., Atlantic salmon).
Larger Organisms
- Fecundity (ability to make many offspring) increases with body size.
- Larger size advantages can include delaying sexual maturity until larger.
Mating & Lifespan
- Example of tradeoff- mating vs lifespan in fruit flies (Drosophila).
- Females that laid eggs had shorter lifespans.
- Males housed with virgins had shorter lifespans, larger males lived longer.
Age Structure Pyramids
- Snapshot of population age structure at a particular point in time.
- Useful in population management, conservation efforts, and for predicting future growth patterns.
Life History Tables
- Summarize age structure, size, life history (reproductive) stage, and survivorship.
- Predict population change over time.
- Useful for managing crops, livestock, conservation, and pest control.
- Includes calculation of survival rate (Sx), survivorship (lx, or proportion of cohort still alive), fecundity (mx), and net reproductive rate (Ro).
Survivorship Curves
- Type I: low mortality until end of life (large animals, high parental care, high juvenile survival)
- Type II: constant rate of mortality throughout lifespan (mix of r and K-selected traits)
- Type III: low juvenile survivorship, mortality rate decreases with age (r-selected)
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Description
Explore the fascinating world of reproductive strategies and parental investment in various species. This quiz delves into the trade-offs between egg number, reproductive seasons, and survival tactics shaped by natural selection. Gain insights into how different reproductive strategies affect offspring survival and population dynamics.
