Grade 12 Reproductive Animal Strategies Flashcards
What is the goal of each species?
Produce maximum number of surviving offspring while using the least amount of energy
Define Courtship
Behaviours designed to attract another animal for mating and breeding
List the three types of simple strategies
Chemical (pheromones)
Visual (bright colours)
Auditory
How does courtship maximise reproduction?
- Ensure males and females find suitable mates
- Sexual behaviour timed so male and female are ready for mating
- Energy expenditure generally by male, so female conserves energy for breeding
Where does external fertilisation take place and in what type of species does it occur?
Takes place in water
Occurs in most aquatic vertebrates
How is the uncertainty of external fertilisation overcome
Large numbers of sperm and eggs are released
In what type of species does internal fertilisation usually occur?
Terrestrial Vertebrates
How does internal fertilisation maximise reproduction?
Gametes closer together
Reduced gamete production saves energy
Define Ovipary
Eggs develop outside of the parent
What is a downside of Ovipary in aquatic creatures, and how is it offset?
High energy input from female for egg production
Offset by less energy being needed for yolk production and parental care
Define Ovovivipary
Internally fertilised eggs are kept inside the female until they hatch
What type of fish is Ovovivipary common in?
Surprisingly common amongst sharks
Does the embryo of an Ovoviviparous species rely on its mother?
No, food comes from yolk of egg.
Only dependent on mother for physical protection
How does Ovovivipary maximise reproduction?
Fewer eggs produced, so lower energy expenditure
Developing embryo less vulnerable
Young are fully developed, so can get their own food
Define Vivipary
Fertilisation is internal and the eggs do not have a shell
How does the embryo of a Viviparous species obtain nourishment?
Obtained continuously from the mother, usually through a placenta
What major evolutionary innovation allowed the first reptiles to colonise dry land?
The Amniotic Egg
How does the amniotic egg maximise reproductive success?
Fluid-filled Amnion protects embryo against dehydration
Allantois is a reservoir for nitrogenous waste in reptiles & birds
Yolk Sac holds nutritious food
Chorion surrounds other membranes
Define Precocial development
Born almost fully developed.
Where does energy expenditure go to for Precocial development?
Pre-natal developments
List four defining traits of Precocial Species
Are born with;
1. Open eyes and have hair or down
2. Large brains relative to body size
3. Are immediately active
4. Are not confined to nests
How does Precocial development maximise reproduction?
Offspring can find own food and look after themselves
Why do many herd animals develop precocially?
Allows the young to keep up with the movement of the herd, which is useful when movement to not overuse a food source is important.
Define Altricial development
Born not well-developed
