Summary
Life Science/ Biology grade 11-12 summary of animal strategies (IEB)
- Course
- Institution
A comprehensive summary of animal strategies from the mind action series textbook (IEB) from an A (80%+) student
[Show more]
Seller
Follow
kiaradurkin4
Reviews received
Content preview
BIOLOGY PRELIMINARY NOTESKIARA DURKIN
REPRODUCTIVE ANIMAL STRATEGIES
The goal of each species
• Produce the maximum number of surviving offspring while using the least amount of energy
= reproductive effort
• Asexual reproduction found in lower and microscopic organisms have a low reproductive
effort
• Sexual reproduction in all vertebrates requires a higher reproductive effort
Strategy: genetically determined behaviour
1. Courtship (behaviour/ signals that are designed to attract another animal for mating and
breeding)
• Simple strategies: chemical (pheromones), auditory or visual (bright colours) stimuli
- Females emit pheromones that indicate that they are ready to mate
• Complex strategies: elaborate and unique to each species
- Females prefer larger, elaborately featured, energetic males
- Females choose better male = reinforces pair bonding (important for parental
care)
How will courtship maximise reproduction?
- Ensure that males and females find suitable mates
- Sexual behaviour timed – both male and female are ready to mate
- Energy exerted by male; females have more energy for breeding
- Increases likelihood of offspring surviving to sexual maturity
2. External vs internal fertilisation
• External fertilisation:
- Most aquatic vertebrates
- All reproductive energy goes to producing eggs
- Not ideal: fertilisation is uncertain; large number of eggs eaten
Strategies to maximise reproduction from external fertilisation:
- Huge numbers of eggs and sperm released (many survive, many are lost to
predators
- Courtship to ensure male and female gametes are close together
• Internal fertilisation:
- Terrestrial vertebrates
- Birds + reptiles breed using their cloaca
Strategies to maximise reproduction from internal fertilisation:
- Gametes placed closely together
Fewer gametes needed – effort can be placed into parental care/ elaborate
gestation/ incubation
3. Ovipary, ovovivipary and vivipary
• Ovipary: eggs develop outside of the parent
- Could be fertilised internally or externally
- Majority of animals are oviparous – egg yolk is the only food source that
developing embryos receive
, - How does ovipary in aquatic environments maximise reproduction?
Embryos well protected
High amount of effort placed into producing and laying eggs
- How does ovipary in terrestrial environments maximise reproduction?
Few eggs produced = more energy to protect + incubate; produce nutrient rich
eggs; allows offspring to be fully formed when hatched
Shell protects against predators, pathogens, damage, and dehydration
• Ovovivipary: eggs are fertilised internally and are kept inside female’s body until
ready to hatch
- Not dependent on mother except for physical protection and gaseous exchange
- Egg richly supplied with yolk
- Occurs in many sharks
- How does ovovivipary maximise reproduction?
Fewer eggs produced, mother expends less energy
Developing embryo much less vulnerable to predation, cold temperatures, and
damage
Young are born fully developed: able to get own food and escape predators
• Vivipary: fertilisation is internal and eggs do not have a shell
- Young are born live
- Obtains nutrition from mother through placenta
- How does vivipary maximise reproduction?
Embryo is nourished and protected
Further energy is expended on parental care
- Chances of offspring surviving = high
4. Amniotic egg
• Amniotes (reptiles & birds/ mammals – do not lay eggs) produce eggs that, after
fertilisation, develop extra-embryonic membranes (amnion, allantois, yolk sac &
chorion) – allow embryo to survive + develop on land
• How does amniotic egg maximise reproductive success?
- Embryonic membranes maximise development of embryo and foetus; allows
offspring to survive harsh conditions more easily
- Fluid filled amnion surrounds embryo: protects embryo from dehydration and
mechanical injury
- Allantois: reservoir for nitrogenous waste in birds + reptiles
- Yolk sac: nutritious food that develops embryo
- Chorion surrounds all membranes:
Birds + reptiles – allows for gaseous exchange
Mammals – forms placenta with endometrium to allow foetus to move safely
5. Precocial and altricial development
• Strategies of development, to increase likelihood that offspring will reach
reproductive age, evolved to:
- Provide nourishment to embryo
- Protect them from predation
• Precocial development:
- Hatch/ are born when fully developed
- Parental energy goes into prenatal care; females less involved after birth
- Precocial species at birth/ hatching:
1. Open eyes and hair
2. Large brains
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying this summary from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller kiaradurkin4. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy this summary for $3.61. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
76669 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy summaries for 14 years now
Recently viewed by you
