Summary Grade 12 Reproductive Strategies - Life Science IEB

JFIN 2019


Reproductive Strategies:
 Successful reproduction is essential to ensure the continued existence of a species.
 Animals use various reproductive strategies to increase their reproductive success.
 Strategies are structural, functional and behavioral adaptations that increase the
chances of fertilization and survival of offspring.
 The success depends on how a species utilizes energy to produce and care for viable
offspring.
 There are 2 types of reproductive strategies:
 R – strategy = spend too much time reproducing, not for parenthood. Thus
many of the offspring die before adulthood.
 K – strategy = produce less offspring but spend copious amounts of time in
parenthood, thus the offspring have a better chance of surviving to
adulthood.
 The following reproductive strategies are discussed:
1. Courtship.
2. External vs Internal Fertilization.
3. Ovipary, Ovovivipary and Vivipary.
4. Amniotic Egg.
5. Precocial and Altricial Development.
6. Parental Care.

Survivorship Curves:




 Type 1 (convex curve):
 High survivorship/low mortality in young individuals.
 Low survivorship/high mortality in old individuals.
 Type 2 (straight line):
 Steady survivorship/steady mortality at all ages.
 Individuals have the same chance of dying at any age.
 Type 3 (concave curve):
 Low survivorship/high mortality in young individuals.
 High survivorship/lower mortality in old individuals.


Courtship:

Reproductive Strategies – Adapted from the Answer Series Part II

, JFIN 2019


 Courtship is the behavoural patterns of male and female animals that lead to mating
and offspring.
 The purpose of courtship:
 Ensures both sexes are ready for mating.
 Helps to identify mating partners of the same species and thus prevent
unsuccessful mating between different species.
 Helps choose a suitable partner – females choose larger, stronger and more
attractive physical features for a male.
 Courtship can take place by using:
 Visual stimuli.
 Sound stimuli.
 Chemical stimuli.
 Physical movements.

Visual Stimuli:
 Best know example is a male peacock who uses his striking, brightly coloured tail
feathers to court the female.
Sound Stimuli:
 Male frogs use sounds to attract the females. Each frog species has its own call.
Females make no sounds, but are attracted by the males calls.
 Male birds also sing to attract females.
Chemical Stimuli:
 In some insects and mammal species, the females secrete chemical substances
(pheromones). This is a signal to males that they are sexually mature.
 Male moths can detect pheromones over long distances.
 Female lions, dogs and cats also secrete pheromones in the air.
Physical Movements:
 Scorpions perform a mating dance to ensure both sexes are ready to mate, if the
dance is successful, mating will occur.
 Male tortoises ‘massage’ the females head, cheeks and neck with vibratory
movements of their long front claws.
 Some male eagles perform acrobatics to impress females – flying high, dives down
and somersaults.
 The male weaverbird builds a nest to impress the female, when the female
approaches, he will flutter around to display his colourful wings.

External vs Internal Fertilisation:
 Fertilization – the fusing of a haploid male gamete (sperm) with a haploid female
gamete (egg/ovum) to form a diploid zygote.
 Two types of fertilization:
 External fertilization.
 Internal fertilization.



External Fertilisation:
 Takes place outside of the females body.


Reproductive Strategies – Adapted from the Answer Series Part II