9_Life History_BI370

Life History

The timing of major life events in a species or organism, shaped by ecological and evolutionary forces.

Survivorship Type I

Indicates that most individuals survive to old age.

Survivorship Type 2

Indicates constant mortality throughout the lifespan.

Survivorship Type 3

Indicates high mortality rates among offspring.

Phenotypic Plasticity

The ability of one genotype to produce different phenotypes under varying environmental conditions.

r-Selected Species

Species that have short lifespans, rapid growth, and produce many small offspring, adapted to unstable environments.

K-Selected Species

Species that have long lifespans, slower growth, and produce few large offspring, adapted to stable environments.

Two-fold Cost of Males

The cost of sexual reproduction where only half of the offspring are productive females due to genetic contribution from males.

Red Queen Hypothesis

The hypothesis that organisms must constantly adapt to survive while interacting with ever-evolving organisms in nature.

Crossing Over

A process in genetics where chromosomes exchange segments during meiosis, resulting in new allele combinations.

Recombination

The process of forming new allele combinations through crossing over during meiosis, which increases genetic variation.

X/Y system

Sex chromosomes in most mammals; XX = female, XY = male

Z/W System

Sex chromosomes in birds; ZW = female, ZZ = male

Undifferentiated sex chromosomes

Sex develops differently under different conditions; amphibeans

Temperature-dependent sex determination

Reptiles

Haplodiploidy

Sex determination in ants; fertilized are female (diploid) and unfertilized are male (haploid)

Isogamy

Gametes are similarly sized and formed

Anisogamy

Gametes are different sizes, typically larger for eggs and smaller for sperm

Benefits of sexual reproduction

Sex helps to combine good alleles; recombination helps to get rid of deleterious mutations; increased genetic diversity combats parasitic infections

Ruby in the rubbish effect

Sexual reproduction allows for the removal of harmful alleles from a population