Breeding for balance
View Sequence overviewStudents will:
- explore how the reproductive strategies of multicellular animals are related to their environment and the complexity of the organism.
- examine how the number of offspring produced by animals is related to the amount of parental care.
Students will represent their understanding as they:
- record and graph data obtained from reproductive models.
- identify animals as r- and K-strategists.
- use argumentation processes in discussions regarding the impact of global warming on reproductive strategies.
In this lesson, assessment is formative.
Feedback might focus on:
- selection and construction of appropriate representations to organise, process, and summarise data and information.
- analysis and connection of data and information to identify and explain patterns, trends, relationships and anomalies.
- analysis of the impact of assumptions and sources of error in methods, and evaluation of the validity of conclusions and claims.
- construction of logical arguments based on evidence to support conclusions and evaluate claims.
- selection and use of content, language, and text features effectively to achieve their purpose when communicating their ideas, findings, and arguments to specific audiences.
Whole class
Breeding for balance Resource PowerPoint
Each group
6-sided die
Counters
Permanent marker (to mark one side of the counter)
Optional: Population growth example spreadsheet
Each student
Individual science notebook
Population growth Resource sheet
Surviving siblings Resource sheet
Lesson
Re-orient
Discuss what is meant by the term ‘offspring’ and how it is preferred by scientists, as ‘babies’ can sometimes be born mature and ready to reproduce within 1-3 weeks (e.g. flies can reproduce within 2 weeks of hatching).
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkIdentifying and constructing questions is the creative driver of the inquiry process. It allows students to explore what they know and how they know it. During the Inquire phase of the LIA Framework, the Question routine allows for past activities to be reviewed and to set the scene for the investigation that students will undertake. The use of effective questioning techniques can influence students’ view and interpretation of upcoming content, open them to exploration and link to their current interests and science capital.
When designing a teaching sequence, it is important to spend some time considering the mindset of students at the start of each Inquire phase. What do you want students to be thinking about, what do they already know and what is the best way for them to approach the task? What might tap into their curiosity?
Read more about using the LIA FrameworkFamilies
Pose the question: How many offspring do different animals have?
- How many offspring does a dog/cat/mouse/frog/cane toad have?
- What is the maximum number of offspring a parent could have at the same time?
- Seahorse fathers and bogong moth mothers can have up to 2000 offspring in a single pregnancy.
- How many offspring does a human have in a single pregnancy? What is the maximum or the minimum?
- Do you think it is easy to have twins, triplets etc.? Why or why not?
(Slide 9) Pose the question: How does the way an animal reproduces affect the survival of...
- ...the parents?
- ...the offspring?
- ...the population?
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkThe Investigate routine provides students with an opportunity to explore the key ideas of science, to plan and conduct an investigation, and to gather and record data. The investigations are designed to systematically develop content knowledge and skills through increasingly complex processes of structured inquiry, guided inquiry and open inquiry approaches. Students are encouraged to process data to identify trends and patterns and link them to the real-world context of the teaching sequence.
When designing a teaching sequence, consider the diagnostic assessment (Launch phase) that identified the alternative conceptions that students held. Are there activities that challenge these ideas and provide openings for discussion? What content knowledge and skills do students need to be able to complete the final (Act phase) task? How could you systematically build these through the investigation routines? Are there opportunities to build students’ understanding and skills in the science inquiry processes through the successive investigations?
Read more about using the LIA FrameworkReproduce for survival
Explain that students are going to do two simulations to explore how the number of offspring born affects animals’ chances of survival.
(Slide 10) Introduce the first activity Population growth Resource sheet. Discuss the assumptions made in this simulation (each parent is fertile, finds a mate outside the population, and only reproduces once), and how these assumptions simplify the model. This will be revisited during the integrate routine.
The population growth simulation compares population growth between animals with a small number of offspring (simulated by flipping a counter to generate 1-2 offspring) and animals with many offspring (simulated by tossing a die to generate 1-6 offspring). The total population only includes the number of offspring that were born during that generation.
Optional: The Population growth example spreadsheet can be used to generate random numbers and to automatically calculate the sum of offspring at each generation.
✎ STUDENT NOTES: Calculate the population growth over 4 generations and draw a line graph displaying the results for both populations. (Slide 11)
- Why do we have random numbers of offspring being born?
- This reflects the variation in the real world.
- If the animals were only selecting mates within the population, what would happen if all the offspring were females?
- The population would become extinct.
- What would happen if each parent produced the maximum/minimum number of offspring? Would the population grow faster or slower? Why or why not?
- If each parent produced the maximum number of offspring, then the population would increase at a faster rate.
- What is happening to each population? How fast are they growing?
- The population that has multiple offspring grows at a faster rate.
- What would happen to the population if each set of parents could breed more than once?
- What would happen if there were some infertile/non-breeding members of the community?
- Do you think this model accurately reflects what happens in a population? Why or why not?
- What are the strengths/weaknesses of this model?
Explain that animals that rapidly reproduce many offspring and use minimal parental care are using what is called the r-reproductive strategy. Animals that produce only a few offspring and spend time caring for them and teaching them how to survive are using the K-strategy of reproduction.
Pose the question: Which strategy is most effective in producing surviving offspring?
(Slides 12 and 13) Introduce the second activity Surviving siblings Resource sheet. Ask students to select one animal information card and identify if the animal is using the r- or K-reproductive strategy, and the number of offspring usually produced. Explain that students should work through the three scenarios and calculate the number of offspring that would survive each scenario. They should do this for three different animals of their choice.
✎ STUDENT NOTES: Calculate the number of offspring that would survive each of the three scenarios. Repeat for two more animals.
r-strategy and K-strategy
r-strategy and K-strategy are two reproductive strategies used to describe how organisms reproduce.
r-strategy and K-strategy are two reproductive strategies used to describe how organisms maximise their chances of survival and reproduction in different environments.
r-strategy
Organisms that follow an r-strategy, such as many insects and small fish, produce a large number of offspring but invest little energy in parental care. These organisms tend to thrive in unstable or unpredictable environments where there is little competition and resources are abundant. Their strategy is to reproduce rapidly to ensure that at least some offspring survive, even though many may not. r-strategists typically have short lifespans, mature quickly, and produce many offspring with minimal parental care.
K-strategy
K-strategists, such as elephants and humans, produce fewer offspring but invest heavily in nurturing them. These organisms are typically found in stable environments where competition for resources is high. They focus on quality over quantity, with longer lifespans, slower growth rates, and more parental involvement. K-strategists tend to reproduce later in life and have fewer offspring, but these offspring have a higher chance of survival due to parental care and investment in their development.
It’s not surprising that many organisms don’t fit neatly into the r- and K-strategy framework. Many species use a mix of both strategies or adjust their approach based on local conditions at any given moment. An organism that can switch between r-strategy and K-strategy may be the most adaptable, as its flexibility allows it to thrive in a wider range of environments
r-strategy and K-strategy are two reproductive strategies used to describe how organisms maximise their chances of survival and reproduction in different environments.
r-strategy
Organisms that follow an r-strategy, such as many insects and small fish, produce a large number of offspring but invest little energy in parental care. These organisms tend to thrive in unstable or unpredictable environments where there is little competition and resources are abundant. Their strategy is to reproduce rapidly to ensure that at least some offspring survive, even though many may not. r-strategists typically have short lifespans, mature quickly, and produce many offspring with minimal parental care.
K-strategy
K-strategists, such as elephants and humans, produce fewer offspring but invest heavily in nurturing them. These organisms are typically found in stable environments where competition for resources is high. They focus on quality over quantity, with longer lifespans, slower growth rates, and more parental involvement. K-strategists tend to reproduce later in life and have fewer offspring, but these offspring have a higher chance of survival due to parental care and investment in their development.
It’s not surprising that many organisms don’t fit neatly into the r- and K-strategy framework. Many species use a mix of both strategies or adjust their approach based on local conditions at any given moment. An organism that can switch between r-strategy and K-strategy may be the most adaptable, as its flexibility allows it to thrive in a wider range of environments
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkFollowing an investigation, the Integrate routine provides time and space for data to be evaluated and insights to be synthesized. It reveals new insights, consolidates and refines representations, generalises context and broadens students’ perspectives. It allows student thinking to become visible and opens formative feedback opportunities. It may also lead to further questions being asked, allowing the Inquire phase to start again.
When designing a teaching sequence, consider the diagnostic assessment that was undertaken during the Launch phase. Consider if alternative conceptions could be used as a jumping off point to discussions. How could students represent their learning in a way that would support formative feedback opportunities? Could small summative assessment occur at different stages in the teaching sequence?
Read more about using the LIA Frameworkr- and K-strategies
(Slide 14) Ask students to identify the advantages of the different r-strategy and K-strategy approaches. Encourage students to provide evidence from their modelling to support their claims of an advantage that helps offspring survive to the next generation.
✎ STUDENT NOTES: Use argumentation processes to make claims about the effectiveness of each strategy in ensuring survival of the population (claim, evidence, and reasoning that link everything together).
- Which strategy was most likely to produce surviving offspring? Why do you think that?
- How quickly would offspring need to ‘grow up/mature’ if their parents used the r-strategy?
- r-strategy offspring usually mature and become independent very quickly.
- How would this be different to the offspring that used the K-strategy?
- K-strategy animals are born very immature and need to grow while in their parents’ care.
- What would happen if a r-strategy population were able to grow unchecked (no predators, plenty of food etc.)?
- The population would quickly become out of control.
Discuss how K-strategy animals tend to learn their survival processes from parents, while r-strategy animals rely on quick maturing and large numbers to survive.
(Slide 15) Revisit the assumptions made at the start of the lesson and discuss the impact of an assumption being incorrect, including:
- each parent is fertile (infertility affects the rate of population growth)
- each individual finds a mate outside the population (if a population has a higher number of males, then the population grows slower as females are needed to carry the young in most species)
- each individual only reproduces once each season (some animals can reproduce more quickly—rats can breed at 6 weeks of age)
Pose the question: Which reproductive strategy would be most affected by global climate change?
Discuss how the climate is changing in your local area, including more droughts, floods, and warmer weather. Discuss how K-strategy animals have longer life spans and tend to live in stable environments. This means the loss of a few animals in an unpredictable environment can affect the parental care of offspring.
✎ STUDENT NOTES: Explain how global warming would impact animals that use either r- or K-strategies.
Reflect on the lesson
Students might:
- research how temperature affects the sex of turtles (and the impact of global warming).
- categorise the remaining animal cards as r- or K-strategists.
- re-examine the intended learning goals for the lesson and consider how they were achieved.