Introducing Individuals and Life Histories

Question 1

What is a unitary organism?

Answer 1

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

Question 2

What is a modular organism?

Answer 2

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

Question 3

What is a population?

Answer 3

A group of organisms of one species that interbreed and live in the same place at the same time

Question 4

Why is the composition of a population important?

Answer 4

Properties of a population can affect population growth and resilience

Question 5

What is the life history of a species?

Answer 5

The typical schedule of survival and reproduction, along with the traits that impact these patterns

Question 6

What key traits underpin life history?

Answer 6

Rates e.g. somatic growth and senescence

Timing e.g. maturation and frequency of reproduction

Allocation e.g. offspring size and number

Question 7

What are ephemeral species?

Answer 7

Plants and animals whose adult lifespan only lasts a few weeks or months

Desert annual plants
Some amphibia

Question 8

What are ephemeral life histories an adaptation for?

Answer 8

Adaptation to living in highly variable, harsh environments

Wait out the bad times and take advantage of the rare ‘good’ conditions (usually < 8 weeks)

Question 9

What are annual life histories?

Answer 9

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

Question 10

What are annual life histories an adaptation for?

Answer 10

Seasonal environments - adapted to avoid harsh winter conditions

Question 11

What are some ways to categorise life histories?

Answer 11

The frequency of reproduction e.g. iteroparous and semelparous

The seasonal timing of reproduction e.g. continuous or seasonal breeding

Question 12

What is iteroparous reproduction?

Answer 12

Reproduction is spread out

Produce offspring during repeated reproductive episodes

Most mammals, majority of perennial plants and many insects

Question 13

What is semelparity?

Answer 13

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

Question 14

What is continuous reproduction?

Answer 14

Reproduction is not tied to a particular season

Question 15

Under the classification scheme of life histories, what can annual life histories be classified under?

Answer 15

They are seasonal breeders and are semelparous

Question 16

What taxa come under seasonal breeders that are iteroparous? What is a difference between them?

Answer 16

Birds and many mammals

Mammals tend to have a longer juvenile phase

Question 17

What animals come under continuous breeder that is iteroparous?

Answer 17

Humans and other primates

Tropical insects

Question 18

What is the difference between life cycle and life history?

Answer 18

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

Question 19

What is an organisms’ life history shaped by?

Answer 19

Natural selection

Question 20

What is a Darwinian demon?

Answer 20

An organism that lives for hundreds for years, reproduces frequently and produces 1000s of offspring in each reproductive bout

Question 21

What is the principle of allocation?

Answer 21

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

Question 22

Why can’t Darwinian demons exist?

Answer 22

Life histories are constrained by external factors (resources, competitors, predators etc) and trade-offs among life history traits

Question 23

What are some trade-offs for life histories?

Answer 23

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

Question 24

What happened to clutch size the following year when eggs were added or removed to the current clutch in Collard Flycatchers?

Answer 24

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