The tortoise and the hare an overview of life history

An organism’s life history is the suite of traits that define its growth, develop, and (most importantly) reproductive activity.

Sexual reproduction usually involves parts that can be identified as “male” and “female”. In most animals, individuals usually have a recognizable gender. Plants often defy gender concepts.

Reproduction generally results in substantial energetic cost

“Switching” in plants: Allocation of resources to either growth or reproduction

Reproductive output is related to size of the parent organism

Reproductive output is influenced by access to resources

Access to resources is determined largely by- 1) habitat

-optimal habitat = more resources, more offspring-marginal habitat = fewer resources, fewer offspring

2) competition- competition with others reduces access to resources- less competition = more offspring

An organism’s life history is the suite of traits that define its growth, develop, and (most importantly) reproductive activity.

• Ecologists, traditionally, refer to life history “strategies.”

• Life history strategies were then classified these into two very broad categories.

K-selected species have long life spans, low reproductive rates, are often slow growing. Slow and steady wins the race

r-selected species are fast growing, with high reproductive rates. They arrive at reproductive maturity very quickly. Live fast and die young

Some features of the “K strategy”

1) Long life span2) Low reproductive rate3) High investment in offspring

• Large seeds• Post-partum attention by parents

4) Low dispersal rates (sometimes)5) Slow growth

Some features of the “r strategy”

1) Short life span2) High reproductive rate3) Low investment in offspring

• Small seeds• Little post-partum attention by parents (your on your own kid!!)

4) Long dispersal distances5) Rapid growth

Organismal life histories span a spectrum of possibilities

• K and r, (and just described) are typical of the endpoints.

• Most of the real world is somewhere in between.

• Many species are a blend of each strategy (some trees grow fast, but live a very long time, with long-distance seed dispersal).

• Many population ecologists are irritated by the r – K concept because they over simplify.

Bristlecone & dandelionan overview of life history